1764 



HUMAN ANATOMY. 



an acquired defect (vide supra), the hernia develops in the presence of causative 

 factors (page 1759). 



Acquaintance with the changes in the abdominal wall and peritoneum involved 

 in the descent of the testis is necessary to an understanding of the anatomy of inguinal 

 hernia. Although these changes are described with the development of the testicle 

 (page 2040), the chief features of the process may be noted here with advantage. 



By the end of the second foetal month the developing testicle lies behind the 

 peritoneum at the side of the upper lumbar vertebra?, the epididymis and later the 

 testicle being attached to a fibro-muscular band, the genito-ingitinal ligament, which 

 stretches from the sexual gland to the lower part of the anterior abdominal wall. 

 During the third month, guided by this attachment, the testicle migrates from its 

 primary location to a position which later corresponds to the internal abdominal ring, 

 About this time the muscular, fascial, and peritoneal layers of the abdominal wall 

 show a protrusion in the inguinal region which results in the production of a sac, 

 the inguinal bursa ; this deepens and extends into the scrotal fold, which meanwhile 

 is formed independently as an integumentary fold. The genito-inguinal ligament, 



FIG. 1485. 



Internal obliqu 



Cremaster muscle 



Aponeurosis of external 

 oblique, turned outward 



Saphenous opening 



Cut edge of aponeurosis of 



external oblique 



Sheath of rectus 



Transversalis fascia 



. Conjoined tendon 



Triangular fascia 



_Spermatic cord 



Dissection of right inguinal canal; aponeurosis of external oblique has been cut and turned outward. 



being attached to the structures undergoing evagination, extends into the inguinal 

 bursa. The muscular tissue within the wall of the latter is derived from the internal 

 oblique and transversalis and constitutes the cremaster. The lining of the inguinal 

 bursa is obviously the direct continuation of the general serous membrane of the 

 abdominal cavity and later constitutes the proccssus -i'a^inalis peritonci. Thicken- 

 ing of the lower end of the genito-inguinal ligament produces an elevation of the 

 floor of the bursa known as the inguinal conns, a structure, however, that in man is 

 very feebly developed as compared with that found in some lower animals. Subse- 

 quently, during the seventh and eighth months, the inguinal conus and the attached 

 testicle are drawn downward into and through the inguinal canal until, shortly before 

 birth, the sexual gland gains its permanent position in the scrotum. The rudimentary 

 conus and the genito-inguinal ligament, which together correspond to the structure 

 usually described as the gubfrnaculttm tfstis, become progressively shorter and 

 smaller as the testicle descends, their remains constituting the scrota/ !ii>-aMcnt< the 

 snivel-mis band which permanently attaches the tunica vaginalis and the testicle to 

 the surrounding tissue of the walls of the scrotum. 



The original retropcritonea] position of the testicle is always retained, this organ 

 and the accompanying constituents of the spermatic- cord descending outside the 



