Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Todd, Robert Bentley
either singly {fig.326. d) or in numbers of three 
four, six, or seven {fig. 326. e). A more con- 
Fig. 326. 
Developing Vesicles of the Spermatozoa from the 
Testicles of the Dog. 
siderable number of them in one common cyst 
is unusual ; but they may, according to K'öl- 
liker's statement, amount to twenty. The size 
of the cyst naturally depends on the number 
and state of developement of the vesicles it 
encloses. Ordinarily it amounts to about 
i /// i /// 
10 0 8 O _ * 
On pursuing the genesis of the vesicles of 
developement, it will be found that they are 
produced in the interior of cells, according to 
the law of endogenous formation. The various 
circumstances which present themselves during 
the microscopical analysis support the proba¬ 
bility of this opinion. It is certainly often 
difficult to determine whether an individual 
vesicle is destined for the production of other 
cells (tochter-Zellen), or immediately for the 
formation of a spermatozoon. But we shall 
see presently that the daughter cells are fur¬ 
nished with the same capacities as the free 
vesicles of developement ; they are like them 
in every respect, and justify the inference of a 
perfect identity with them. Wherever, there¬ 
fore, we find these free vesicles of developement, 
they have, in our opinion, likewise been pro¬ 
duced in the interior of other cellular forma¬ 
tions, and have only become free by the dis¬ 
solution of the former. The real process of 
formation of the spermatozoa in the interior of 
the vesicles of developement cannot be reached 
by our observation. The spermatozoon does 
not possess at its commencement those sharp, 
distinct contours—that great refracting power, 
which afterwards so much distinguish it. Like 
a slight linear shadow it is seen lying in the in¬ 
terior {fig. 327. a, b) ; in addition to which it 
Fig. 327. 
A 1 B C D 
Spermatozoa of the Dog in the interior of the 
developing Cell. 
is covered by the granules, which are so readily 
deposited from the liquid part of the con- 
tents. It is only gradually that it assumes a 
distinct appearance. At first the body only 
is seen, being recognisable by its specific 
form. The tail becomes visible subsequently. 
The entire spermatozoon lies in a curved 
shape close to the wall of the vesicle, until it 
has reached its full developement, when it be¬ 
comes free by the bursting of the vesicle of 
developement. Sometimes {fig. 327. c,d) indi¬ 
vidual vesicles may be seen, from which the 
tail of a spermatozoon is projecting, whilst the 
body is still situated in the interior. The vesicle 
of developement generally retains, however, 
its original round shape, even when the sper¬ 
matozoon has reached its perfect developement, 
and begins to stretch itself. Angular vesicles 
of developement, which occur so frequently 
in other animals, probably never occur here. 
It is only in rare cases {fig. 327. d) that the 
vesicle extends itself into a thin tail-like 
appendix, which then encloses the posterior 
part of a spermatozoon, and which is 
evidently only produced by the stretching 
of the latter. A law, which K'olliker first 
pronounced as correct, may here be enume¬ 
rated, viz. that only one single spermatozoon, 
and never a greater number, is developed in 
each vesicle of developement. 
The formation of the spermatozoa takes 
place in exactly the same way in the vesicles 
of developement, even in those cases where the 
latter have not become free, but remained 
enveloped by their mother cells. The sper¬ 
matozoa, in this case, are not, however, im¬ 
mediately set free by the dissolution of 
the vesicles of developement ; but they ar¬ 
rive, first of all, in the cavity of the ex¬ 
ternal cyst. The number of the enclosed 
spermatozoa therefore depends on the num¬ 
ber of the enclosed vesicles of develope¬ 
ment, a single fibre only being formed in 
each vesicle. The presence of several sper¬ 
matozoa in the interior of a vesicle, therefore, 
affords us an immediate proof, that the latter 
histologically possesses the function of a 
mother cell, and is not itself the vesicle of 
But likewise in this case the process ter¬ 
minates with the dissolution of the cyst that 
surrounds the spermatozoa, and which pre¬ 
vented their becoming free immediately after 
the dissolution of the vesicle of developement. 
According to analogy with other animals* 
it is very probable that the above men¬ 
tioned association of groups of the sperma¬ 
tozoa into fascicles is caused by the longer per¬ 
sistency of the vesicles of developement in the 
interior of a common mother cell. At all 
events, such an occurrence is traceable in 
almost all other cases in which a similar asso¬ 
ciation in groups takes place; and it also 
happens among the mammalia, to judge from 
the fact, that a delicate cyst-like enclosure is 
often perceived at the circumference of the 
Aves. — The spermatozoa of birds possess 
uniformly, instead of the short oval and flat¬ 
tened body which distinguishes them in 
mammalia, a body of a long and slender


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