THE UROGENITAL SYSTEM 
135 
follicle and forming the stratum granulosum, (3) a thickened mass 
of follicular epithelial cells surrounding the ovum and forming the 
cumulus oophorus, and (4) a fluid, the liquor folliculi, which fills 
the cavity of the follicle and becomes finally very great in amount 
(to serve the mechanical function of carrying out the ovum when 
the follicle ruptures). 
Select with care a good section through an ovum in a large 
follicle, and study the ovum to identify (a) the cell membrane or 
zona pellucida, ( b ) the cytoplasm containing yolk (small in 
amount in the mammals) and constituting the vitellus, (c) the 
nucleus, known as the germinal vesicle, and ( d ) the nucleolus, 
known as the germinal spot. Draw a typical section through a 
large follicle , showing its parts and the parts of the ovum. 
3. The Testis (Lab. SI. Coll.). 
Study under the low power of the compound microscope, 
transverse sections of the mammalian testis, stained by some 
method which will bring out cells in mitosis. Note that the 
section consists of a large number of smaller sections, mainly 
transverse, of the numerous seminiferous tubules of which the 
testis is chiefly made up while there is also a small amount of 
intertubular connective tissue in which are present large cells 
known as the interstitial cells. In the walls of the tubules all 
stages of developing male germ cells may be seen. Carefully select 
for study under high power sections of different tubules which show 
the following stages of development of the male germ cells, 
noting particularly which of these stages occur simultaneously 
in a given tubule: 
(a) Spermatogonia, the small cells which lie in contact with the 
basement membrane of connective tissue forming the outer wall of 
the tubule. 
( b ) Primary spermatocytes, formed by the growth of certain of 
the spermatogonia. 
(c) Secondary spermatocytes, formed by the division of each of 
the primary spermatocytes into two daughter cells; they are there¬ 
fore half the size of the primary spermatocytes and twice as 
numerous. 
