15*
A STUDY OF THE FUNCTION OF THE EPIDIDYMIS
III. FUNCTIONAL CHANGES UNDERGONE BY SPERMATOZOA
DURING THEIR PASSAGE THROUGH THE EPIDIDYMIS AND
VAS DEFERENS IN THE GUINEA-PIG
BY WILLIAM C. YOUNG.
(Arnold Biological Laboratory, Brown University.)
(Received zist September, 1930.)
(With One Text-figure.)
INTRODUCTION.
IN two recent papers (Young, 1929 a, b) attention was directed to the fact that,
in mammals, spermatozoa which appear to have attained their full structural
development while still attached to the germinal epithelium, are compelled to pass
through the long coiled ductus epididymidis before they reach the vas deferens
where they are in a position to be discharged. It was noted further that, while the
significance of the epididymis for spermatozoa and the nature of changes undergone
by spermatozoa during their passage through this organ have been subjects of
experimentation by numerous investigators, current opinions with respect to these
questions are both numerous and varied.
Among other opinions, the suggestions had been made (1) that certain developmental changes which are important for the successful functioning of spermatozoa
are attributable to some specific action of the epididymal secretion (Tournade,
1913; Stigler, 1918; Braus and Redenz, 1924; Redenz, 1924, 1925 a, b, 1926;
von Lanz, 1924 b, 1926), and (2) that the epididymis is a reservoir functioning to
preserve the vitality of spermatozoa stored in it until the time of their discharge
(Van der Stricht, 1893; Tournade and Delacarte, 1913; Braus and Redenz, 1924;
Redenz, 1924, 1925 a, b, 1926; von Lanz, 1924 a, b, 1926). These opinions have
since been reaffirmed and extended (von Lanz and Malyoth, 1928; von Lanz,
1929; Redenz, 1929; Redenz and Belonoschkin, 1929; and Belonoschkin, 1929 a, b).
What appeared to be a defect in the first of these theories was the fact that
certain developmental changes, such as the acquisition of the capacity for being
stimulated to motion and, to some extent, the increased capacity for resisting high
temperature, which are undergone by spermatozoa during their passage through
the epididymis, represent nothing more than a continuation of changes which are
occurring while the spermatozoa are still contained in the testis (Young, 1929 a).
Such being the case, it seemed unnecessary to postulate the existence of some
stimulus to spermatozoon development in the epididymis which is not present in
152
W I L L I A M C. YOUNG
the testis. The second theory, to the effect that the epididymis functions to preserve
the vitality of spermatozoa until the time of their discharge, was questioned after
it had been found that any preserving action possessed by the epididymal secretion
is powerless to prevent the ageing of spermatozoa which normally seems to follow
the attainment of their maturity (Young, 1929 b).
Because of these objections to the older conceptions of the epididymal spermatozoon relationship, a new theory was formulated as far as this was possible on the
basis of the experiments which had been performed. It was suggested that the
epididymis provides an environment in which stimuli to spermatozoon development which are not different from those found in the testis are present; that spermatozoa require more time for the completion of their development than they have
before they are loosened from the germinal epithelium; that they are, therefore,
carried into the epididymis as immature or unripe cells which are incapable of
functioning; and that much of the time consumed by them in passing through the
epididymis is necessary for the completion of their development. Once functional
maturity has been attained, however, there is no influence which preserves them
indefinitely and, unless they are discharged, they age and become at first incapable
of effecting fertilisation and finally incapable of being stimulated to motion. In
other words, it was suggested (1) that the developmental changes which occur in
spermatozoa during their passage through the epididymis are not conditioned by
some specific action of the epididymal secretion, but are inherent in the protoplasm
of the spermatozoa themselves, and (2) that emphasis should be shifted from the
conception of the epididymis as a spermatozoon reservoir acting to preserve
spermatozoa which have attained a certain level of development in a state of static
maturity to the conception of the epididymis as an organ of spermatozoon development in which these cells are constantly changing; ripening until an optimal functional capacity is attained and then ageing if their residence is prolonged.
As indicated in a brief, preliminary communication (Young and Simeone, 1930),
confirmation and extension of these suggestions have come from two groups of
experiments. The first involved a study of the reproductive capacity of spermatozoa
removed from two different levels of the epididymis of the guinea-pig under normal
and experimental conditions. A description of the methods which were employed
along with an enumeration of the results which were obtained, and a discussion
of the application of these results to the problem as a whole, form the contents of
this paper.
The second group of experiments involved an investigation of the fate of nonejaculated spermatozoa. The observations made during this part of the study are
reported elsewhere (Simeone and Young, 1931).
EXPERIMENTAL.
The changes which occur in the reproductive capacity of spermatozoa as they
pass through the epididymis were determined by means of the artificial insemination
of females with spermatozoa from two levels of the epididymis under normal and
experimental conditions. If it is true, as has been supposed, that spermatozoa
A Study of the Function of the Epididymis
153
enter the epididymis as immature cells which ripen and acquire their capacity for
effecting fertilisation as they pass through this organ, the percentage of fertile
inseminations when younger spermatozoa from the proximal end of the epididymis
are used should be less than the percentage of fertile inseminations when older
spermatozoa from the distal end are used.
';'.:X\£~-
'•'y--$'&~ •'•=•'&':??: '•;
Fig. i. Testis, epididymis, and proximal end of vas deferens from guinea-pig as seen when retracted
into the abdominal cavity, a.. .b is line of separation of cauda epididymidis into proximal and distal
portions from which younger and older spermatozoa respectively were removed from normal males.
Lines c, d, and e represent location of ligatures in experimental males.
The procedure which was employed in testing this hypothesis was as follows:
Whenever two or more females came into heat simultaneously the epididymides
from a normal male were separated along the line a.. .b, Fig. i. Each part was then
macerated in a quantity of Locke's solution so selected that the densities of the
resulting spermatozoon suspensions would be as nearly equal as possible. A light
ether anaesthesia was then administered to the females to be inseminated, and
approximately f c.c. of the suspension introduced into the body of the uterus by
means of a glass catheter. In this way one female was inseminated with spermatozoa
from the proximal end of the cauda epididymidis, and the other with spermatozoa
154
W I L L I A M C. YOUNG
from the distal end of the cauda epididymidis from the same male. The females^
were then held ventral side up for 5 minutes, after which they were numbered and
placed in cages reserved for experimental animals. From the fifteenth to the
twentieth days inclusive after the insemination, each female was examined twice
daily for rupture of the vaginal closure membrane or other signs of a recurrent
oestrum. If such had not occurred by the twentieth day, the female was regarded
as pregnant and kept isolated until the end of the gestation period, at which time
the size and condition of the litter were noted. Any irregularities such as stillbirths, abortions, and intra-uterine resorptions were also recorded.
At the time of insemination samples of the spermatozoon suspensions were
examined microscopically. It is of interest, in connection with a point to be
mentioned later that, without exception, the spermatozoa removed from the distal
end exhibited a more vigorous motion than those removed from the proximal end.
Ninety-nine females were inseminated with spermatozoa removed from the
proximal portion of the cauda epididymidis, and ninety-seven were inseminated
with spermatozoa removed from the distal portion. Of the former, thirty-three, or
33'3 P e r cent., were impregnated. Of the females inseminated with spermatozoa
from the distal end, sixty-six, or 68 per cent., were impregnated. The doubling of
the number of fertile inseminations, when spermatozoa from the distal portion
of the epididymis were used, may be attributable either to the greater maturity of
spermatozoa from the distal end or to the maturity of a much larger number of
spermatozoa from this portion of the epididymis. In either case the difference is
believed to provide ample evidence for the developmental nature of changes which
occur in spermatozoa during their passage through the epididymis. The opinion
that these changes are inherent in the spermatozoa rather than conditioned by some
specific action of the epididymal secretion has been expressed. Additional evidence
will be cited elsewhere in the paper.
The suggestion (Young, 1929 b) that spermatozoa within the epididymis which
have attained an optimal functional maturity are not preserved indefinitely, but
soon begin to undergo regressive or degenerative changes, was tested by a modification of the above described procedure.
Following an abdominal incision and the retraction of the testis and epididymis
into the body cavity, it was possible to ligature the head of the epididymis in one
place, c, and the vas deferens in two places, d and e, without interfering with the
vascularisation of the structures involved. The testes were then replaced in the
scrotal sacs. Provided no adhesions developed, the males were killed 20 and 25
days later, and spermatozoa removed from the proximal and distal ends of the cauda
epididymidis as before. At this time samples of the spermatozoon suspensions
were examined microscopically.
It was found that the condition of the tubules 20 or 25 days after the operation
is never similar to that at the time of the operation, provided the ligature of the
head of the epididymis has been complete. Most of the tubule proximal to the
line a.. .b has been emptied, and the portion of the tubule distal to the line a.. .b
has become conspicuously distended with spermatozoa which have been forced
A Study of the Function of the Epididymis
155
Pnto it from the proximal levels. Despite this condition it is easily possible to remove
spermatozoa from the proximal and distal portions of the column without the contamination of either.
It was expected, if the course of changes undergone by spermatozoa during
their residence in the epididymis is similar to that which had been postulated, that
the younger spermatozoa contained in the proximal end of the cauda epididymidis
at the time of the operation would mature, develop the capacity for a more vigorous
motion and become more capable of effecting fertilisation. Similarly, it was expected that the older, mature or ripe spermatozoa contained in the distal end of
the cauda epididymidis at the time of the operation would age, become weakened
in their capacity for being stimulated to motion, and become less capable of effecting
fertilisation. In short, it was expected that the conditions with respect to the
strength of motility and the capacity for effecting fertilisation would be reversed
from what they had been when spermatozoa from normal males were used.
Forty-three females were inseminated with spermatozoa from the proximal end
of the spermatozoon column, and forty were inseminated with spermatozoa from
the distal end of the column. Of the former, nineteen, or 44-2 per cent., were impregnated. Of the females inseminated with spermatozoa from the distal end of
the column, thirteen, or 32-5 per cent., were impregnated. In most cases, spermatozoa
removed from the proximal end of the column were as active or conspicuously
more active than those from the distal end of the column. As was expected, therefore, spermatozoa which have been isolated in the epididymis for 20 days show
a reversal of the conditions which exist in the normal epididymis. Spermatozoa
at the proximal end of the column can be stimulated to a more vigorous motion,
and are more successful in effecting fertilisation after 20 days' isolation in the
epididymis than those from the distal end of the column in the same animals.
This reversal of the normal relationship was even more striking in the case of
spermatozoa which had been isolated 25 days. In this part of the experiment ninetyeight females were inseminated with spermatozoa from the proximal end of the
column, and one hundred females were inseminated with spermatozoa from the
distal end of the column. Of the former, forty-eight, or 49 per cent., were impregnated. Of the females inseminated with spermatozoa from the distal end of
the column, twenty-five, or 25 per cent., were impregnated.
The data described above are summarised in the two upper lines of Table I.
Based upon actual reproductive capacity, which is unexcelled as a measure of general
fitness, they reveal more clearly than any data obtained heretofore the course of
changes which can occur in spermatozoa during their residence in the epididymis.
Developmental changes culminating in the attainment of an optimal condition for
effecting fertilisation are the first to occur. They are followed by regressive changes
which result in a loss of the capacity for effecting fertilisation. Proof that developmental changes occur came from the fact that the younger spermatozoa removed
from the proximal end of the epididymis were successful in effecting fertilisation
in but 33-3 per .cent, of the cases, while older spermatozoa removed from the distal
end of epididymides from the same males were successful in effecting fertilisation
156
W I L L I A M C. YOUNG
in 68 per cent, of the cases. Further proof came from the fact that the ability or'
the younger spermatozoa to effect fertilisation increased from an approximate
normal of 33-3 per cent., under the conditions of the experiment, to 44-2 per cent,
at the end of 20 days' isolation in the epididymis and to 49 per cent, at the end of
25 days' isolation. Proof that regressive changes set in following the attainment of
an optimal functional capacity came from the fact that the ability of the mature
spermatozoa located in the distal end of the epididymis to effect fertilisation decreased from an approximate normal of 68 per cent., under the conditions of the
experiment, to 32*5 per cent, following 20 days' isolation in the epididymis and
to 25 per cent, following 25 days' isolation.
Table I. Summary of data obtained following insemination offemales with spermatozoa
removed from proximal and distal ends of normal and ligatured cauda epididymides.
Normal males (control)
Proximal
end
Number of inseminations
Fertile inseminations (%)
Average litter size
Number of normal indiNumber of still-born individuals
Number of aborted and resorbed individuals
Still-born individuals (%)
Aborted and resorbed individuals (%)
99
33'3
1-85
48
Distal
end
97
680
260
20-day ligature
Proximal
end
Proximal
end
Distal
end
43
40
98
44-2
32'5
2-S8
490
23
72
43
9
6
250
139
32
7
13
2
2
15
12-3
36
Distal
end
25-day ligature
10 ±
2±
6
2-34
100
25-0
2-36
21 ±
9±
10-7
18-8
7-8
48
82
9'4
90
22-7
2O-O
20-9
Whether or not the fertilising capacity of spermatozoa from the proximal end
of the column would have increased further, and that of spermatozoa from the
distal end of the column would have decreased further with 30 days' isolation
is not known. It is planned to determine this in an extension of the investigation.
That the reversal of the spermatozoon relationships referred to above was not
more complete at the end of 25 days may be attributable to certain factors which
could not be controlled, namely, a constant interchanging and shifting in position
of spermatozoa within the epididymis. Whether or not there is any active motion
of spermatozoa within the epididymis which might be partly responsible for this
is not known, although Redenz and von Lanz claim that spermatozoa within the
epididymis are capable of independent motion. It may be instead that younger
spermatozoa are constantly being forced into the distal part of the epididymis and
vas deferens to mix with the older spermatozoa by the distally directed muscular
pressure. In addition, the removal of old spermatozoa in the epidjdymis and vas
deferens by liquefaction, which is now known to occur there (Simeone and Young,
A Study of the Function of the Epididymis
157
I931), may leave places which are filled by viable spermatozoa from the proximal
regions of the tubule.
An observation of interest, in connection with the suggestion that the development of spermatozoa which takes place during their passage through the epididymis
is inherent in their protoplasm rather than conditioned by simuli originating in
the epididymis, was made on the testes removed from certain males 20-25 days
after the ligature of the head of the epididymis. Many such testes contained
numerous patches of white seminiferous tubules which bore a striking resemblance
to the small portion of the tubule of the cauda epididymidis proximal to the line
a.. .b in the figure. When these white tubules were removed, macerated in Locke's
solution, and studied microscopically, they were found to contain many active
spermatozoa. This condition was in marked contrast to that found in the seminiferous tubules from a normal testis, where only an occasional spermatozoon can
be stimulated to exhibit the weakest flagellation of its tail. It is, however, similar
to that found in the testis of the albino rat (Young, 1929 a), where many spermatozoa
capable of being stimulated to motion can be found.
It is suggested that the great increase in the number of such spermatozoa which
can be stimulated to motion and the great increase in the strength of their motility
are attributable to the greater maturity of these cells which have been unable to
pass from the testis into the epididymis. Presumably, their development has continued despite their retention in the testis. The observation that this continuation
of development is not dependent upon the passage of the spermatozoa into the
epididymis provides further evidence against the idea of a specific action of the
epididymal secretion on spermatozoon development. The extent to which spermatozoa isolated in the testis in this manner can develop is not known.
The data (Table I) which have to do with litter size and condition are meagre,
since only 204 of the 477 inseminated females were impregnated. They are presented, however, for what they suggest in the way of future experiments rather
than for any conclusions which may be drawn from them at this time.
Average litter size was smallest, 1-84, among that group of females inseminated
with the youngest spermatozoa, namely, those from the proximal end of the cauda
epididymidis from normal males. It rose to 2-60, when older spermatozoa from
the distal end of the cauda epididymidis were used. It remained near this level,
2-50 and 2-58, when spermatozoa which had been isolated 20 days were used, and
decreased slightly to 2-34 and 2*36 when spermatozoa which had been isolated
25 days were used. In experiments which are now in progress an attempt is being
made to determine if the smaller litters, which seem to follow inseminations with
the youngest and oldest spermatozoa, are attributable to the fertilisation of a smaller
number of ova or to an unusually large number of intra-uterine resorptions.
The number of still-born individuals on the one hand, and the number of
individuals aborted or resorbed within the uterus on the other hand, were recorded
separately. The percentage of still-born individuals will be noted to be fairly
constant throughout, and as high among the females inseminated with the youngest
spermatozoa as among those inseminated with the oldest spermatozoa. The perjEB-vmii
11
158
W I L L I A M C. YOUNG
centage of individuals which were aborted or resorbed, on the other hand,
somewhat lower, 3-6 and 9 per cent., among the controls than it was, 18-8 to 22-7
per cent., when the older spermatozoa were used. It is of interest to note that many
of these individuals showed gross structural defects.
The question arises: is this larger number of abortious cases of intra-uterine
resorption and foetal abnormalities which occurred following the insemination of
females with the older spermatozoa due to the age of the spermatozoa which were
used ? Imperfect development has been suggested as a consequence of the fertilisation of the eggs of certain invertebrates by old spermatozoa (Dungay, 1913, for
Nereis; Medes, 1917, for Arbacia), but whether this also applies to the guinea-pig
can be determined only after more data have accumulated from experiments now
in progress.
The uniform frequency with which still-born individuals were born to females
in all groups compared with the variation in the frequency with which abortions
and intra-uterine resorptions occurred, suggests that these gestational abnormalities
may be two different phenomena traceable to different causes rather than being
expressions of the same phenomenon differing only in the time of occurrence.
The still-births may be a consequence of parturitional difficulties associated,
possibly, with the size of the foetus or its position within the uterus. Abortions
and intra-uterine resorptions may have, on the other hand, a germinal origin.
Again, it is expected that experiments which are now being undertaken, will dispose
of this problem one way or another.
DISCUSSION.
The data which have been obtained from the experiments described above and
from earlier experiments (Young, 1929 a, b) furnish a basis for an evaluation of the
divergent theories of the epididymal spermatozoon relationship held by contemporary workers (Rendenz, von Lanz, Belonoschkin, and Young, loc. cit.).
Redenz and Belonoschkin seem to be of the opinion that all internal or protoplasmic changes undergone by spermatozoa during their development, occur while
these cells are still attached to the germinal epithelium. These changes include the
development of the capacity for independent motion. The spermatozoa are then
loosened from the germinal epithelium, and swim by means of their own strength
through the rete tubules and vasa efferentia into the ductus epididymidis. At this
time the spermatozoa are mature internally, but unprotected externally from the
effects of injurious factors in the environment, such as acids and high temperature,
which act to decrease the intensity and duration of motion. As they pass through
the epididymis, however, they become enclosed in a microscopically invisible protective envelope {Oberfldchenhdutchen or Hulle) composed of epididymal secretion.
This adherent layer of secretion provides the external protection they require, and
thus imparts to them a greater resistance against the action of injurious factors
which they may encounter. In other words, Rendenz and Belonoschkin would
seem to be of the opinion that the ripeness or maturity attained by spermatozoa
A Study of the Function of the Epididymis
159
during their passage through the epididymis is a quality conditioned by the presence
of the epididymal secretion around the spermatozoon, and is not a development
inherent in the spermatozoon.
An equally important part of their theory concerns the provision made for the
preservation of spermatozoon vitality until the time of an ejaculation. This is said
to be accomplished by the limitation of the ability for independent motion which
spermatozoa contained in the epididymis are assumed to possess, a condition which
prevents the dissipation of the energy available for motion in useless movements.
This limitation of motion, in turn, is thought to be accomplished by some action
of the high carbon dioxide tension and the low oxygen tension which are consequences of the density of the stored spermatozoa. Restoration of the motile
condition is believed to be brought about at the time of an ejaculation, possibly
by the oxygenation which occurs, and possibly by the alkalinity of the prostatic
and seminal vesicle secretions with which the spermatozoa become mixed.
In only one place does Redenz (1926, p. 135) suggest that the vitality of spermatozoa may not be preserved indefinitely.
Der Begriff "Reifung" hat aber noch einem anderen Inhalt. Nachdem ich zugleich
mit v. Lanz mit ganz verschiedenen Methoden feststellen konnte, dass der Nebenhoden
ein Organ ist, das lebende Samenfaden speichern kann, ist die Frage, in welchem Zeitpunkt das Spermium nach seiner Entstehung zur Befruchtung kommt, von wesentlicher
Bedeutung geworden. Es ist damit zum erstenmal die Frage angeschnitten, welchen
Einfluss auf die Bewegungsdauer, auf die Zeugung, ja auch auf die Vererbung und die
Geschlechtsbestimmung eine solche Uberreife im mannlichen Organ hat. Zwar werden
Spermien, die sehr lange im Nebenhodenschweif verweilen, hochstwahrscheinlich auch
an ihrem Sekretmantel Schaden leiden und damit weniger Aussichten haben, zur Befruchtung zu gelangen. Jedenfalls ist zu der Frage des Eialters, bei der Befruchtung,
vom Follikelsprung angerechnet, die des Spermienalters, gemessen von der Abstossung
aus der Sertolizelle an, hinzugetreten.
This suggestion does not seem to be incorporated in the theory of the function
of the epididymis expressed in more recent papers, however, and it is difficult to
conclude how much importance he attaches to it.
The most recent theory of the epididymal spermatozoon relationship advanced
by von Lanz (1929) is similar in many respects to that formulated by Redenz. Like
the latter, von Lanz is of the opinion that spermatozoa move out of the testis by
means of their own motion, that important ripening changes occur during their
passage through the epididymis in consequence of some specific action of the
epididymal secretion, and that the preservation of spermatozoon vitality during the
residence of these cells in the epididymis is accomplished by the limitation of their
motion. Unlike Redenz, he believes that a considerable buffering action of the
epididymal secretion must be carried over to the protoplasm of the spermatozoon
during storage in the epididymis, that ripening events take place inside the cell
protoplasm and not around it, that the limitation of motion is accomplished by the
natural acidity of the epididymal secretion rather than by any excess of carbon
dioxide or deficiency of oxygen, and in no place does he suggest that spermatozoon
vitality may not be preserved indefinitely.
160
W I L L I A M C. YOUNG
Many observations made in the course of experiments performed by the writer
are at variance with certain of the more important assumptions and conclusions
which are a part of the theories of the epididymal spermatozoon relationship
advanced by Redenz and von Lanz. It is doubtful, first of all, on the basis of many
observations on testes from bulls and rams (Young, 1929 a), if spermatozoa exhibit
an independent motion while they are still contained within the seminiferous tubules,
or take any active part in their movement into the epididymis. Only the weakest
vibratile movement of the tail has ever been detected by the writer following the
maceration of testis fragments in Locke's solution, a flagellation which has never
been observed to result in progressive motion. Furthermore, spermatozoa removed
from distal parts of the epididymis are activated more quickly than those removed
from proximal levels. If spermatozoa do move into the epididymis by means of
their own strength, and if their motion is limited gradually by the nature of the
environment found within this organ, one would expect that spermatozoa in the
distal end of the structure where their motion is most completely limited, would
be the last rather than the first to be activated. The nature of the epididymal
secretion may be such as to prevent the occurrence of motion, but it probably does
not limit motion which once existed.
A second point emphasised by Redenz and von Lanz, which is questioned on
the basis of data reported previously (Young, 1929 a) and in this paper, is that
developmental changes undergone by spermatozoa during their passage through
the epididymis are conditioned by some specific action of its secretion. It has been
found, for example, that the extent to which spermatozoa removed from the seminiferous tubules can be stimulated to motion varies from species to species. In a
preparation from the testis of the rat, hundreds of motile spermatozoa can be seen.
In preparations from the testes of the bull, ram, and guinea-pig, on the other hand,
only an occasional spermatozoon, which exhibits the weakest vibratile movement
of the tail, can be seen. Evidently, in some species under normal conditions, a
certain portion of the developmental process occurs only after the spermatozoa
have been carried into the epididymis, whereas, in other species, corresponding
changes occur while the spermatozoa are still within the testis.
It has also been observed that the number of spermatozoa which can be stimulated to motion, following their removal from the testis, is often much greater when
the escape of spermatozoa from the testis has been prevented by the ligature of the
head of the epididymis than it is when the testis is normal. From this it would
seem, that in any given animal, many of the developmental changes which normally
occur after the spermatozoa have entered the epididymis will occur while these cells
are still contained in the testis, if their passage from the testis into the epididymis
is prevented.
If the above described observations have been interpreted correctly, the older
conception of spermatozoon development as consisting of two processes, one of
which occurs in the testis and the other of which occurs only in the epididymis,
seems questionable. It is suggested instead, that spermatozoon development is a
single continuous process occurring in part in the testis and in part in the epididymis,
A Study of the Function of the Epididymis
161
and that the extent to which development occurs in the testis or in the epididymis
depends, not upon one set of stimuli in the testis and upon another set in the
epididymis, but rather upon the proportion of the total developmental period spent
in each of the two organs.
A third criticism of the theories advanced by Redenz and von Lanz is that
neither makes proper allowance for the fact noted elsewhere (Young, 1929 b, and
others) and in this paper, that regressive as well as developmental changes may
occur in spermatozoa during their passage through the epididymis. Inclusion of
this fact in any theory of the epididymal spermatozoon relationship is important,
not only to complete the account of the post-testicular history of spermatozoa,
but also because certain problems are raised which otherwise would be overlooked,
and which may prove of some importance for the part played by the male in reproduction.
What would appear to be the most important of these centre around the rate
of progress of spermatozoa through the epididymis, viz. how much time is required
for the passage of spermatozoa through the epididymis? To what extent does this
rate of progress vary from male to male? To what extent is it modified by the
frequency of copulation and by other factors? Do differences exist in the physiological condition of discharged mammalian spermatozoa similar to those noted by
Lillie (1915) and by Goldforb (1929 a, b, c, and earlier papers) in sea-urchin
spermatozoa? If such differences exist in mammalian spermatozoa, can they be
related to differences in the rate of passage of spermatozoa through the epididymis ?
Lastly, if such differences exist in discharged mammalian spermatozoa, are they
important for any reproductive qualities of the male mammal?
Most of these questions are now being investigated, and it is expected that the
answers, when such are obtained, will supplement the theory of the epididymal
spermatozoon relationship elaborated in this and the following paper (Simeone
and Young, 1931).
CONCLUSIONS.
1. By means of experiments which have involved the artificial insemination of
female guinea-pigs with spermatozoa removed from different levels of the ductus
epididymidis and observations on spermatozoa confined in the seminiferous tubules,
further evidence has been obtained for the conclusion (1) that the time consumed
by spermatozoa in passing through the epididymis is necessary for a completion
of their development, (2) that the changes undergone during this period represent
a continuation of changes which start while the spermatozoa are still attached to
the germinal epithelium, and are not conditioned by some specific action of the
epididymal secretion, and (3) that in case the spermatozoa are not discharged or
lost in some other manner, regressive or degenerative changes follow the attainment
of an optimal functional capacity.
2. Evidence has been obtained for the existence of a constant distally directed
current of spermatozoa through the epididymides of males even in the absence
162
W I L L I A M C.
YOUNG
of copulations. The importance of determining this rate of progress of spermatozoa
through the epididymis is emphasised on account of its possible relationship to
the physiological condition of ejaculated spermatozoa.
3. The greater frequency with which abortions and intra-uterine resorptions
occurred among females inseminated with older spermatozoa has been noted, as
was the fact that several of the foetuses lost in this manner showed gross structural
defects.
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