196 THE STRUCTURE OF MAN 



MALE GENITAL GLANDS (DBSCENSUS TESTICULOKUM) 



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 coelom 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 Eodents ; 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 is 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 Muridse, 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 obliquus 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 ligamentum inguinale (which 

 must not be confused with the gubernaculum or round ligament 

 of earlier writers) is 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, i.e. 

 to that point which corresponds with the aperture of the canalis 

 inguinalis interna. This " ligament," for which a parallel exists 



