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testis, and is named the head or globus major (fig. 235, e) ; the lower, which is more
pointed, is termed the tail or globus minor (e') ; whilst the intervening portion is
named the bod//. The convex surface of the epididymis and the thin anterior border
are free, and covered by the tunica vaginalis. The concave surface, or that directed
towards the testis, is also free, except at the upper and lower ends, and invested by
the same tunic, which here forms a pouch between the epididymis and the outer face
of the testicle, and nearly surrounds the epididymis, except along its posterior
border, which is united to the gland by a duplicature of the serous membrane,
containing numerous blood-vessels. At its upper and lower extremity, the
epididymis is attached to the testis by fibrous tissue and a reflection of the tunica
vaginalis, the globus major also by the efferent ducts of the testis.

At the back of the testis and epididymis, beneath the fascia propria, opposite
the lower two-thirds of the testis, is a considerable amount of unstriped muscular
tissue, the inner muscular tunic of Kolliker.

On the front of the globus major, somewhat to the outer side, there are usually
found one or more small pedunculated bodies covered by an extension of the tunica
vaginalis and formed mainly by connective tissue and blood-vessels. These are the
hydatids of Morgagni. They are commonly regarded as remains of part of the foetal
structure termed Miiller's duct. One of them, cf a more regularly pyriform shape,
and more constant than the rest, lies closely between the head of the epididymis and
the testis.

This has been thought, but as it would appear on insufficient evidence, to be the homolog-ue
of the ovary in the male sex (Fleischl, Krause). Its surface is ciliated, and a canal lined by
ciliated epithelium and opening into the cavity of the tunica vaginalis is sometimes contained
within it.


The testis is enclosed in a strong capsule, the tunica albuginea. This is a
dense unyielding fibrous membrane, of a white colour, and of considerable thickness,
which immediately invests the soft substance of the testis, and preserves the form of
the gland. It is composed of bundles of fibrous tissue, which interlace iu every
direction. The outer surface is covered by the tunica vaginalis, except along the
posterior border of the testis, where the spermatic vessels pass through and the
two extremities of the epididymis are attached.

In the interior, the tibrous tissue of the tunica albuginea is prolonged from the
posterior border for a short distance into the substance of the gland, so as to form
within it an incomplete vertical septum, known as the corpus Hiyhmori, and named
by Astley Cooper mediastinum testis. It extends from the upper nearly to the
lower end of the gland, and it is wider above than below. The firm tissue of which
it is composed is traversed by a network of seminal ducts, and by the larger blood-
vessels of the gland, which are lodged in channels formed in the fibrous tissue.

From the front and sides of the coipus Highmori numerous slender fibrous



cords and imperfect septa of connective tissue are given off in radiating directions,
and are attached by their outer ends to the internal surface of the tunica albuginea

(Modified from Kblliker.)

a, seminiferous tubes, converging at 6, to the mediastinum ; e, rete testis ; d, vasa efferentia ;
e, epididymis ; h, section of vas deferens ; i, tunica albuginea, sending septa into the body of the
testis ; c.v., cavity of tunica vaginalis.

at different points, thus incompletely dividing the glandular substance into lobules.
According to Kolliker, plain muscular fibres are prolonged upon these septula.
The whole internal surface of the tunica albuginea is covered by a multitude of

The true length and diameter of the ducts have been disregarded in this as well as in the preceding
figure, a, a, tubuli seminiferi coiled up in the separate lobes ; b, vasa recta ; c, rete vasculosum ;
d, vasa efferentia ending in the coni vasculosi ; e, f, g, convoluted canal of the epididymis ; h, vas deferens;
i, i, section of the back part of the tunica albuginea with fibrous processes running between the lobes.

fine blood-vessels, which are branches of the spermatic artery and veins, and are
held together by a delicate areolar web. Similar delicate ramifications of vessels



are seen on the various fibrous offsets of the mediastinum, upon which the blood-
vessels are thus supported in the interior of the gland. This vascular network,
together with its connecting areolar tissue, constitutes the tunica vasculosa of
Astley Cooper.

Seminiferous tubules. The glandular substance of the testis which is
included in the fibrous framework formed by the albuginea, the mediastinum, and
the trabeculee, is a mass of convoluted tubules known as the tubuli seminiferi,
which are somewhat loosely connected together by areolar tissue into the lobes or
lobules above mentioned. Of these lobes there are some 100 to 200 (Krause) or more ;
they are of unequal size, the middle ones being the larger, and are imperfectly

lobuli testis


rete testis


& epididymis

tubuli recti

vas deferens


separated from one another, the septa being incomplete. In each lobe are two,
three, or more seminiferous tubules closely convoluted, and here and there branched,
especially at their anterior or distal extremity, where, in a cortical zone near the
albuginea, they are stated to communicate frequently laterally with one another.
It is not difficult to unravel the tubules for some distance, for their walls are
moderately strong, and their diameter (0'2 mm.) large compared with those of other
tubular glands, such as the kidney. Their length is estimated to be on an average
rather greater than two feet (60 cm.) and their number between 800 and 900
(Lauth). They have a smooth contour, but this is interrupted at intervals by
small bulgings, which are more numerous near the commencement of a tubule than
near its termination. The walls of the seminiferous tubules are composed of several
layers of flattened cells. Of these only the innermost layer is complete, being-
formed of epithelioid cells closely united edge to edge into a basement membrane.
This is strengthened by the other layers, which, however, exhibit intervals between
the flattened cells which compose them, these intervals becoming very marked in
the outermost layers. In consequence of their being thus formed of several layers,,
the walls of the tubules have a concentrically striated appearance in cross-section.


The tubules are occupied by an epithelium which consists , of several irregular
layers of cells, amongst which the seminal filaments or spermatozoa may be observed
in different stages of development (fig. 239). In different tubules of the same test is
and even in parts of the same tubule the condition of development of the spermatozoa
may be very various, and the epithelium presents corresponding differences both in
the number of its layers and the appearance of the cells.

preparation by Mr. A. Eraser.) Magnified.

a, with the spermatozoa least advanced in development ; 6, more advanced ; c, containing fully
developed spermatozoa. Between the tubules are seen strands of interstitial cells with blood-vessels
and lymph-spaces.

Structure of the spermatozoa. A spermatozoon is a minute filiform particle
about 0'055 mm. long, consisting of three parts : a nucleus or head, a middle piece
or body, and a spontaneously vibratile .tail. In man the head is of a flattened oval


Fig. 240. HUMAN SPERMATOZOA (Retzius).

1, in profile, the tail not represented ; 2, viewed on the flat ; 6, head ; c, middle-
piece ; d, tail ; e, end-piece of the tail.

shape, appearing pointed when seen in profile and with a depression on
each flattened surface. A minute barb-like projection has been described
at its extremity (Dowdeswell) ; this is however much more apparent in
some animals. The head stains intensely with nuclear dyes, and is
mainly formed of chromatin (nuclein). It is about 0*0045 mm. long,
0*0025 mm. broad, and 0*0015 mm. thick. In certain animals it is
invested with a clear mantle termed the head-cap (Schweigger-Seidel),
but this is not easily apparent in man in the completed stage. The
head also varies greatly in other respects in different animals, its shape
and size being characteristic for each species.

The middle piece or "body of the spermatozoon is nearly cylindrical
in man. It is about 0*006 mm. long and less than 0*001 mm. in
diameter. It is difficult to make out any structure in it in man, but in some
animals (mouse, rat), a spiral thread can be seen closely coiled around its
periphery, whilst through its centre a filament passes which appears to be a
prolongation of a central filament within the tail and which ends close under
the base of the nucleus or head in a globular enlargement known as the terminal
globule or globuloid body.

VOL. III., FT. 4. Q



The tail is about 0'045 mm. long, and finer than the middle piece. It tapers
towards the extremity. Near its termination it becomes abruptly finer and its
terminal sixth (end-piece of Retzius) is an extremely delicate fibre, which under
certain circumstances can be seen to be composed of three or more of the finest
possible fibrils. This end-piece is apparently a direct combination of the central
filament of the tail, which is elsewhere invested by a sheath, but is here bare. The
distinction between sheath and central filament cannot be made out in the human
spermatozoon. In some animals (newt) an undulating membrane with a fine fibre
running along its free margin is attached spirally by one border along the whole
length of the tail (Leydig) : a similar membrane has been described in man
(Gribbes, W. Krause, v. Bardeleben). The motion of the spermatozoon is a forward
one produced by a spirally lashing movement of the tail, similar to the movements

fibrils of axial filament. fibrils of marginal filament


point of head . . .
fibril of axial filament
marginal fibril . . . J

enlargement of axial
filament in head
(globuloid body) .


marginal fibril . . .

axial fibre ....
undulatory membrane _

... end piece of tail

8. membrane of tail

Fig. 241. DIAGEAM OF A SPERMATOZOON. (Bb'hm and v. Davidorff.) All the parts here shown have
not been made out in the human spermatozoon.

of the cilia of zoospores of bacilli. It may last under favourable conditions for
several days after discharge (4 to 9 days, Piersoll).

Several varieties of human spermatozoa have been described, differing from one another
chiefly in size. Some are occasionally found which are very much larger than usual
(075 mm. long and '0035 mm. broad). According to the observations of K. v. Bardeleben
(Verhandl. d. Anat. Gesellsch., 1891), founded partly on his own preparations, partly on those
of E. M. Nelson, the head of the human spermatozoon consists of several portions, viz., spear.
head-cap, and a main part divided into anterior and posterior portions. The xjtmr, the
existence of which appears to be rather doubtful, is described as an immeasurably fine process
unsymmetrically placed, which may be twice as long as the head. Its tip is recurved and
hooklike. At its base is an elongated particle staining more deeply than the rest. The
head-cap is clear and very delicate. The anterior part of the head is clear, the posterior
part cross striated. A protoplasmic fringe extends from the anterior part to the body of the
spermatozoon. Within the head is a clear refractive particle (globuloid), not staining with
ordinary dyes. A short melt unites the head to the body or middle piece of the spermatozoon.
Both this and the tail (except the end-piece of Retzius) have a frilled membrane along one
side: the tail has a special membrane on the opposite side. The tail contains a central
filament which extends through the body and head and may be traced even into the spear.

Structure of the epithelium of the seminiferous tubules. Of the cells
forming the epithelium of the seminiferous tubules, there are, in most tubules, three
several kinds, differing in situation, in size, and in structure. Those of the first
kind, which are termed the outer or lining cells (spermatoyonia) form the outermost
zone. They are cubical or somewhat flattened cells disposed in a single regular
layer next to the basement membrane of the tubule. In some tubules one of these
cells may here and there be seen to be elongated and to project between the cells
of the next zone, where it comes into connection with a group of developing
spermatozoa. Indications of karyokinetic division are also met with in the cells
of this layer in certain tubules (fig. 242, 6). In the early foetal condition the



spermatogonia are the only cells found in the tubule. The cells of the next zone
become formed from them by karyokinetic division.

The cells of the second kind, intermediate or spermatogenic cells (spermatocysts of
some authors), form a middle or intermediate zone in the tubules. They are large
clear cells with conspicuous nuclei, the latter invariably exhibiting some stage of
karyokinesis. They lie one, two or more deep, varying in different tubules according
to the condition of development of the spermatozoa, and the thickness of the layer
they form varies accordingly. When two or more deep, the groups of developing
spermatozoa and the elongated spermatogonia with which the groups are connected
penetrate between them and tend somewhat to break the continuity of the layer.

(This diagram is chiefly founded upon the drawings of H. H. Brown.)

, lining epithelium cells, seen dividing in 6 ; a', sustentacular cells ; 6, spermatogenic or mother-
cells, with skein-like nuclear filaments : these cells are seen actively dividing in 5 ; c, spermatoblasts,
forming an irregular column or clump in 6, 7, 8, and 1, and connected to sustentacular cell, a', in
2, 3, 4, and 5. In 6, 7, and 8 advanced spermatozoa of one crop are seen between columns of spermato-
blasts of the next crop, s', parts of the spermatoblasts which disappear when the spermatozoa are fully
formed ; s, seminal granules, probably resulting from the disintegration of *' ; a", in 1 and 2, are
nuclei of sustentacular cells, which are probably becoming extruded.

These spermatogenic cells, which are originally derived from the spermatogonia,
themselves give origin by two or more stages of karyokinetic division to the cells of
the next layer or spermatoblasts, but some of the cells resulting from the first
division are not converted into spermatoblasts. These remain as a layer of sperma-
togenic cells, ready in due time to produce by further division the next crop of
spermatoblasts. 1

The third kind of cell in the seminiferous tubule is the spermatoblast. The
spermatoblasts (spermatids of some authors) are derived as just stated from division
of the spermatogens or spermatocysts, and on the other hand are directly trans-

1 According to Brown all the spermatogenic cells or spermatocysts are converted, after division,
into spermatoblasts, and fresh spermatocysts are produced for the next crop of spermatoblasts by
division of some of the lining cells or spermatogonia.

Q 2


formed into spermatozoa: hence they were termed by H. H. Brown, young spermatozoa,
They form in most tubules an innermost zone of small closely packed granular-
looking and ill-defined cells, which appear blended into a continuous mass (fig. 239, c) r
they are, however, not so blended, but are quite discontinuous. Their nuclei are
small and do not stain deeply with reagents : they show no signs of proliferation.
In some tubules these cells are already becoming elongated (fig. 239, a), and in the
various tubules of the same testis every stage of transformation is met with between
them and the fully developed spermatozoa. As this transformation proceeds they
are seen to collect into definite groups (fig. 239, b) which penetrate between the cells-
of the intermediate layer, and become connected with and imbedded in cells of the
outer layer (sustentacular cells) which elongate to receive them (fig. 242). These
sustentacular cells in alt probability subserve a nutritive function for the developing
spermatozoa. When the development is approaching completion the group of
spermatozoa moves again towards the middle of the tubule, the connection with the
outer layer becoming gradually longer and more attenuated until finally the heads
of the fully developed spermatozoa form a complete zone next to the lumen of the
tubule, into which their tails project, being bent sharply round and extending for a
short distance along the course of the tubule (fig. 239, c ; 242, 1, a).

While this gradual transformation of spermatoblasts into spermatozoa is going
on in a tubule, a fresh crop of spermatoblasts is being formed in the same tubule to
take the place of those thus transformed. This crop is formed as before by
proliferation of the spermatogenic cells which have remained next to the lining
layer, 1 and hence it happens that in the same tubule at least two phases of develop-
ment of spermatozoa or of spermatoblasts are constantly to be seen. But after the
completion of one crop of spermatozoa, the spermatoblasts, which are to become
transformed into the next crop, remain quiescent until the first crop has been dis-
charged. The spermatogenic cells divide at first each into two, and thus form a
first generation. This division takes place by what is termed by Flemming the
" heterotypical form " of karyokinesis, the split chromosomes long remaining con-
nected at their ends, and the stage of metakinesis being greatly prolonged. During
the dyaster phase a second longitudinal splitting occurs, and the daughter-nuclei
again divide immediately, without entering into a resting condition, and without a
further splitting of the chromosomes, to form the nuclei of the cells of the third
generation. The cells of this third generation have, therefore, only half the
typical number of chromosomes in their nuclei, and these are the cells which become
transformed into spermatoblasts. In the final division, therefore, it appears that
the number of chromosomes, or chromatic segments of the nucleus, becomes, by
failure of the usual longitudinal cleavage, reduced to one half the number usual in*
the cells of the particular species of animal under observation. The resulting
nuclei, therefore, of the spermatoblasts resemble, in this respect, the nucleus of the
ovum after extrusion of the second polar globule, and it is only on the conjunction
of the two within the fertilized ovum that the typical number of chromosomes is

The process of reduction of chromosomes in the final division of the spermatic cells was
first shown by 0. Hertwig to occur in Ascaris, and it has since been established for the
salamander (by Flemming 1 ) and some other animals. It has been thought to be of general
occurrence, but this cannot as yet be regarded as conclusively proved, especially in mammals,
in which the observation of the number and changes of the chromosomes is extremely difficult.

Transformation of the spermatoblasts into spermatozoa. The fully
formed spermatoblasts, or spermatids, are small, granular cells, with round nuclei.

1 Or which have. been formed by a new karyokinetic division of the spermatogonia (see note on>
previous page).




In developing into spermatozoa, these become elongated. The nucleus alters in
shape and passes towards one end of the cell, where it forms the head of the
spermatozoon. Within the protoplasm a filament begins to form, sooif growing out
beyond the rest of the cell as the tail. The protoplasm of the cell partly remains to
form the body or middle piece ; partly becomes detached and disintegrated, as the
maturation of the spermatozoon is completed.

Changes in the nucleus. The nucleus of the spermatoblast is at first spherical*



with a somewhat faint outline. It
shows the usual network of a resting
nucleus, but has comparatively little
tendency to stain with dyes (poor in
chromatin). As development proceeds
it becomes at first oval, then conical,
then greatly elongated and compressed,
so that no structure can be seen within
it. In the meantime its chromatin
becomes increased, and finally forms a
dense mass, which gradually takes on
the shape and position of the head of the future spermatozoon.

Changes in the protoplasm. Within the body of the cell but near the nucleus
various structures can be made out (Moore), viz. the archopJasm, a clear or nearly
clear portion of the protoplasm which may contain a vacuole, the so-called chromatic
body, a small mass of darkly staining material close to the nucleus and probably a

Fig. 244. Two STAGES (A AND B) IN THE


Highly magnified.

, archoplasm (Nebenkern)having a vacuole
e, in A ; b, centrosomes ; c, chromatic body ;
Ek, (in B) modified nucleus ; h, head cap.

detached portion of its chromoplasm,

and the centrosome which is usually

double (fig. 244, A). As the nucleus

passes towards the inner end of the

cell, with its pointed end projecting

beyond the general circumference,

and the base directed towards the

centre of the cell, the body of the cell

becomes elongated, assuming first an

oval and then a pear shape, with the

nucleus embedded in the smaller end

of the pear. The centrosome (fig. '

244, b) lies near the base of the

nucleus, in contact with it, and perhaps included within the nuclear membrane

(Hermann), probably taking part in the formation of the so-called " globuloid body."

In connection with this (but whether formed from the nucleus, from the centrosome,

or from the protoplasm of the cell, is not clear), a thread axial filament begins

to appear in the protoplasm, and is soon seen to emerge from the opposite or larger

end of the pear-shaped cell, the protoplasm of which is probably continued over it.


This filament is the rudiment of the " tail," and gradually elongates. It is not clear
how the head-cap is formed, but probably from nucleoplasm, this being perhaps
itself covered by clear protoplasm. The spermatozoon is now developed, but the
middle piece is still large and pyriform, and its peripheral portion forms a projection
which partly encircles the tail (fig. 243). The projection in question disappears in
the further course of development, being partly absorbed into the rest of the middle
piece and into the tail, partly becoming detached and disintegrated. It contains
some deeply staining granules, which are founds mingled with the spermatozoa when
these are set free (spermatic granules).

Interstitial tissue of the testicle. The tissue which connects the semi-
niferous tubules is in some respects peculiar. It consists of fine fasciculi and
laminae of areolar tissue, these being covered by and partly composed of flattened
epithelioid cells. Between the laminas and fasciculi are large cleft-like spaces,
containing lymph, and almost everywhere enclosing the basement membrane of
the tubules. If these spaces are injected by the puncture-method, the injecting
fluid flows away by the lymphatics of the spermatic cord. It is found to penetrate
between the incomplete outer layers of the membrane of the tubules, but is arrested
by the innermost layer.

The blood-vessels are conducted at first along the trabeculas, and from these they
pass into the angular interstices between the tubules. Here they are supported by
the areolar tissue, and accompanied and often completely surrounded by tracts of
peculiar epithelium-like polyhedral cells somewhat like the cortical cells of the
suprarenal capsules, and, like these, often containing yellowish granules. They are

Online LibraryJones QuainQuain's Elements of anatomy (Volume 3:4) → online text (page 28 of 44)