244 SPECIAL HISTOLOGY. 



of the cavernous and spongy bodies, and of the tunica media 

 of the arteries of those parts; in consequence of which 

 the tissue, like a sponge which has been compressed, ex- 

 pands and becomes filled with blood. The rigidity ensues so 

 soon as the muscles are completely relaxed and the sinuses 

 filled to the utmost, without there being any necessity that 

 the return of the blood should be impeded and the circulation 

 stopped. It ceases when the muscles again contract, the 

 venous spaces become narrowed, and the blood is expressed 

 from them. In the act of ejaculation, the ischio-cavernosi, 

 and the bulbo-cavernosus muscles, which are formed of trans- 

 versely striated fibres, increase the rigidity of the anterior 

 parts by the compression of the root of the penis and dorsal 

 veins; but under no circumstances can they, of themselves 

 alone, contribute to the bringing about of the erection. I am 

 not aware that any more important function can be assigned 

 to the helicine arteries; this much being certain, that the 

 erection does not depend upon them, because they do not 

 occur in every part of the human penis, and are wanting in 

 many animals. 



[The investigation of the male sexual organs presents, gene- 

 rally speaking, no great difficulties. The tubuli seminiferi are 

 very readily isolated, and when they are carefully unfolded some 

 divisions are always met with. In order to trace their entire 

 course, they must be injected according to the directions of 

 Lauth or Cooper, which may be found quoted in all Manuals of 

 anatomy. Lauth places the testicle for two or three hours in 

 lukewarm water, then expresses the semen as completely as 

 possible from the epididymis, and immerses the gland for 3 — 4 

 hours in a solution of carbonate of ammonia, or for 8 — 12 

 hours in a saturated solution of carbonate of potass, or a weak 

 solution of caustic potass, which reagents partly dissolve the 

 spermatic cells and epithelia ; the testis is then again com- 

 pressed, laid in alkaline water, and injected with quicksilver, at 

 first under a weak and afterwards under a stronger pressure, 

 a process requiring from 1^ to 2 hours. So soon as the quick- 

 silver has penetrated into the vas deferens, the column must be 

 lowered to 5", for otherwise the tubuli seminiferi, the filling of 

 which demands some hours more, burst. Cooper injected from 



