658 



OF SECRETION. 



hitherto mentioned. The external forms presented by these glands through- 

 out the Animal kingdom, are extremely various ; but their composition is for 

 the most part very uniform. The object is sometimes attained by a simple 

 but much elongated canal ; sometimes by shorter branched tubes ; and in 

 other instances, again, by numerous aggregated coeca, which are often rounded 

 into cells. In regard to this, as to many other glands, it may be stated that, 

 whilst its general form in Insects is that of prolonged tubes, the required ex- 

 tension of surface is given in the Mollusca by the multiplication of cells, so 

 that the structure has a compact spongy character. It is interesting to remark 

 that, in some of the lowest Fishes, this organ consists of a mass of vesicles 

 which have no efferent duct; and that the secretion formed within these 

 escapes by the rupture of the vesicles, allowing it to escape into the abdomi- 

 nal cavity, whence it passes by openings that lead directly to the exterior. 

 In these Fishes, the ova are discharged from the ovarium in a very similar man- 

 ner ; a modification of which plan is followed in all the higher Vertebrata, 

 the ovum being in them also discharged, by the rupture of its containing vesi- 

 cle or ovisac, into the abdominal cavity, but being immediately received and 

 conveyed away by the funnel-shaped internal prolongation of the external ori- 

 fice, which is known as the fimbriated extremity of the Fallopian tube.* 



a. The Testis in Man has in every respect, however, a distinctly glandular character. It 

 consists of several lobules, which are separated from each other by processes of the tunica 

 albuginea that pass down between them, and also by an extremely delicate membrane (de- 

 scribed by Sir A. Cooper under the name of tunica vasculosa) consisting of minute ramifica- 

 tions of the spermatic vessels united by areolar tissue. Each lobule is composed of a mass 

 of convoluted Tiibuli Seminiferi, throughout which blood-vessels are minutely distributed. 



[Fig. 258. 



[Fig. 259. 



The Testicle injected with mercury; 1, tunica 

 albuginea ; 2, seminiferous tubes; 3, the rete vas- 

 culosum testis ; 4, a globule of mercury which has 

 ruptured the tubes ; 5, the vasa efferentia which 

 form the coni vasculosi, G, coui vasculosi forming 

 the head of the epididymis; 7, epididymis ; 8, glo- 

 bus minor of the epididymis; 9, vas dcferens.] 



A view of the minute structure of the Testis ; 

 1, 1, tunica albuginea; :>. 0, corpus highmorianum; 

 3, 3, tubuli seininiferi convoluted into lobules; 4, 

 vasa recta ; 5, rete testis ; 6, vasa efferentia ; 7, 

 coni vasculosi constituting the globus major of 

 the epididymis; ;-, body of the epididymis; !>, its 

 globus minor; 10, vas deferens 11, vasculum 

 aberrans or blind duct.] 



See Principles of General and Comparative Physiology, G41. 



