1000 



DEVELOPMENT OF THE GENERATIVE OEGANS. 



ture attached inferiorly to the lower part of the scrotum, and surrounding the peri- 

 toneal pouch above, which may be distinguished as the gubernacular cord, both this 

 and the plica gubernatrix being included in the general term gubernaculum testis 

 (J. Hunter). The gubernacular cord consists ef fibres which pass downwards from 

 the sub-peritoneal fascia, others which pass upwards from the superficial fascia and 

 integument, and others again which pass both upwards and downwards from the 

 internal oblique muscle and the aponeurosis of the external oblique ; it exhibits, 

 therefore, a fusion of 'the layers of the abdominal wall. Superiorly, it surrounds 

 the processus vaginalis, without penetrating the plica gubernatrix; and the pro- 

 cessus vaginalis, as it grows, pushes its way down through the gubernacular cord and 

 disperses its fibres. By the time that the testis enters the internal abdominal ring, 

 the prccessus vaginalis has reached a considerable way into the scrotum ; and, as the 

 testis follows, the plica gubernatrix becomes shorter, till it at last disappears; but it 

 cannot be said that the shortening of the plica is the cause of the descent of the 

 testicle, and much less (as has been held by some) that the muscular fibres of the 

 gubernacular cord are the agents which effect this change of position. The arched 

 fibres of the cremaster muscle make their appearance on the surface of the processus 

 vaginalis as it descends, while its other fibres are those which descend in the guber- 

 nacular cord. (See for a further account of this process, and the various views which 

 have been held with regard to the descent of the testicles, Cleland, " Mechanism of 

 the Gubernaculum Testis." Edinburgh, 1856.) 



The External Organs of Generation. In the human subject, these have for some 

 time the same form in both sexes ; but, in animals in which the penis is prolonged to 

 the umbilicus, that circumstance forms one of the very earliest sexual distinctions, 

 inasmuch as the clitoris hangs free. 



Fig. 695. DEVELOPMENT OP THE EX- 

 TERNAL SEXUAL ORGANS IN THE MALE 

 AND FEMALK FROM THE INDIFFERENT 

 TYPE (from Ecker). 



A, the external sexual organs in an 

 embryo of about nine weeks, in which 

 sexual distinction is not yet established, 

 and the cloaca still exists : B, the same 

 in an embryo somewhat more advanced, 

 and in which, without marked sexual 

 distinction, the anus is now separated 

 from the urogenital aperture : C, the 

 same in an embryo of about ten weeks, 

 showing the female type : D, the same 

 in a male embryo somewhat more ad- 

 vanced. Throughout the figures the 

 following indications are employed; pc t 

 common blastema of penis or clitoris ; 

 to the right of these letters in A, the 

 umbilical cord ; p, penis ; c, clitoris ; cl, 

 cloaca; ug, urogenital opening; a, anus; 



I s, cutaneous elevation which becomes labium or scrotum ; I, labium ; s, scrotum ; c 0, 



coccygeal elevation. 



Up to the fifth week, according to Tiedemann, there is no separate genito-urinary 

 orifice, and indeed no anus. Previous to this period, or about the beginning of the 

 fourth week, there is a common opening, for the intestine, the generative, and the 

 urinary organs, i. e., a cloacal aperture. In front of this simple opening, there soon 

 appears a small recurved projecting body, which, as it enlarges, becomes grooved 

 along the whole of its under surface. This is the rudimentary clitoris, or penis, at 

 the summit of which an enlargement is formed which becomes the glans. The 

 margins of the groove seen on its under surface are continued backwards on each 

 side of the common aperture, which is now elliptical, and is bounded laterally by 

 two large cutaneous folds. Towards the tenth or eleventh week a transverse band, 

 the commencing perinceum, divides the anal orifice from that of the genito-urinary 

 passage, which latter now appears as a rounded aperture, placed below the root of 



C. 



D. 



