TEE GENITAL ORGANS OF TEE MALE. 961 



of this vaginal membrane — and which are generally described in anatomical 

 treatises, with the two serous layers, as the envelopes of the testicle — are four in 

 number. Reckoning them from within to without, they are the fibrous tuny,, 

 cremaster muscle, dctrtos, and scrotwn. 



Fibrous Tunic {infuadibulform fascia). — This forms the most complete 

 covering to the tunica vaginalis, extending, as it does, over the whole surface 

 of the parietal serous layer, to which it is closely adherent. Very thin, especially 

 at the points corresponding to the cremaster, this membrane is continuous, 

 around the upper inguinal ring, with the transversalis fascia, of which it is only 

 a dependency ; its external face is in relation with the cremaster and dartos. 



Cremaster (or cremasteric fascia). — This .muscle is usually described as an 

 envelope of the testicle, by the name of tunica erythroides. In the domesticated 

 animals it is a bright-red band, attached, above, to the inner or peritoneal sur- 

 face of the ilio-lumbar aponeurosis ; it descends into the inguinal canal, envelops 

 outwardly only the middle portion of the tunica vaginalis, and expands below on 

 the ctd-de-sac, where its fibres terminate by small tendons, which are inserted 

 into the external surface of the infundibuliform fascia. Therefore it is that 

 the envelope the cremaster forms is very incomplete — the greater portion of the 

 testicle, and the inner side of the cord, being left unprotected by this muscular 

 tunic. It is in relation, inwardly, with the fibrous membrane, to which it is 

 united by a plentiful connective tissue ; externally, it is related to the posterior 

 wall of the inguinal canal and the dartos. (It is a connective dependency of 

 the internal oblique muscle.) 



It is the contraction of the cremaster that causes the sudden ascent of the 

 testicle. 



Dartos. — The tissue composing this tunic is contractile ; it is constituted by 

 a mixture of elastic tissue and unstriped muscular fibres. The dartoi'c tunic 

 does not reach the inguinal canal ; consequently, it does not cover that part of 

 the tunica vaginalis. It forms a pouch below the inguinal ring, and is spread 

 from around the margin of this on to the neighbouring parts, to which it adheres 

 somewhat closely ; it is prolonged, gradually thinning, into the sheath of the 

 penis, and even on to the penis itself, and to the tunica abdominalis, as well as 

 between the thighs. The two pouches it forms are quite independent of each 

 other, never becoming confounded, though placed in contact on the mesial line 

 to form a double partition (septum scroti), the leaves of which are separated 

 above for the passage of the penis. The dartos is in relation, inwardly, with 

 the fibrous and erythroid tunics, from which it is isolated by an abundance of 

 lamellar connective tissue,^ which is very condensed towards the globus major 

 epididymis, and forms at this point a kind of cord that passes from the fibrous 

 tunic to the dartos, adhering strongly to each. Externally, the dartos is covered 

 by the scrotum. 



This tunic determines the vermicular movements of which the scrotum is 

 the seat. It wrinkles the skin of the scrotum, and makes it firm and dense, thus 

 aiding the cremaster in raising the testicle. When it is not in a state of con- 

 traction, the skin of the scrotum is smooth and even, and the testicle pendulous. 



Scrotum. — The different membranes enumerated above are double, one 

 being for each tunica vaginalis ; but the scrotum constitutes a single pouch, 

 enveloping the two testicles at the same time. It is merely the portion of skin 



' The testicle is disengaged by tearing tlirough this tissue, in castration by the " covered 

 operation." 



