196 THE STRUCTURE OF MAN 
MALE GENITAL GLANDS (DESCENSUS TESTICULORUM) 
Among Mammals the genital glands of the male (testes) 
agree in their place of origin with those of the female (ovaries). 
Both are developed out of the germinal epithelium, differentiated 
near the dorsal wall of the ccelom to the right and left of the 
vertebral column. But while, during further development, the 
ovaries, as a rule, shift down towards the pelvis, the testes may 
wander still farther (descensus testiculorum). This descensus is. 
closely connected not only with the history of the testis, as the 
result of interaction between the organ and the parts immedi- 
ately surrounding it, but also with the relations of the testis to 
other organs more or less remote from it. 
Many variations occur among Mammals in the manner of 
descent of the testis, and in the changes in the ventral body wall 
which accompany it. It seems possible, however, as Klaatsch 
has shown, to reduce these variations to a simple ground plan. 
The descent of the testes, which is a new development peculiar 
to Mammals, is effected in its most primitive manner in 
Insectivores and Rodents; and everything points to the fact 
that it was originally a periodic phenomenon occurring in the 
adult. For instance, in the Hedgehog the testes retain their ori- 
ginal intra-abdominal position up to the rutting period; but as 
that period approaches they come to lie in evaginable portions of 
the inguinal body wall. After the rutting season they always 
return into the abdominal cavity, but the mechanism by which 
this 1s accomplished is not yet clearly understood. 
In connection with the shifting of the testis, a structure 
termed by Klaatsch the “conus inguinalis” is of the greatest 
significance. This organ is best developed in the Muride, and 
consists of a conical invagination of the muscular abdominal wall, 
at first connected not with the three lateral abdominal muscles, 
but only with the obhquus internus and transversus. Its 
internally projecting point, or at least its surrounding tissue, fuses 
with a cord-like structure called by Klaatsch the ligamentum 
inguinale (cf. Fig. 105). This hgamentum inguinale (which 
must not be confused with the gubernaculum or round ligament 
of earher writers) 1s a subperitoneal strand containing smooth 
muscle, which arises, in both sexes, on each side of the genital 
ducts, and runs to the inguinal region of the abdominal wall, 1. 
to that point which corresponds with the aperture of the canalis 
inguinalis interna. This “ligament,” for which a parallel exists 
