16 ANlMAt CASTBATION. 



condition, and may be closely drawn up into the In- 

 guinal canal, when it assumes a thickly wrinkled 

 surface. 



The second envelope, the dartos, is a prolongation 

 of the tunica abdominal is, and is a yellow, fibrous 

 structure, forming two distinct sacs resting upon each 

 other, and lying on the inside of the scrotum, to which 

 it is intimately adherent. 



In the lateral and superior parts the adhesions are 

 looser, and in front it becomes continuous with the 

 suspensory ligament of the sheath, which, like itself, 

 forms a portion of the abdominal tunic. Under the 

 dartos is a layer of very loose cellular tissue, the 

 lamellffi of which are so formed that it m^ay be divided 

 into several superimposed layers. This formation 

 endows the testicle with great mobility in the dartoid 

 sac ; and these layers may be easily separated with 

 the finger from the external surface of the fibrous 

 coat beneath, except posteriorly, where it forms a 

 strong band which sometimes requires even the aid 

 of an instrument to divide. 



The next envelope is represented by the tunica 

 erythroida which is the cremaster muscle, and from 

 the lumbar region extends itself downwards into the 

 inguinal canal along the outside of the cord, and ter- 

 minates towaixls the superior part of the testicle in 

 fibres spreading only over its external face. This 

 muscle, by its deep surface, rests upon the fibrous 

 coat — another envelope of the testicle and of the cord 

 — and to which it is closely adherent. To the power- 

 ful coatractioa of this muscle is due the retraction 



