114 PKILOSOI'HICAL TRANSACTIONS. [aNNO 1/04. 



Had the known structure of the testes, m relation to their excretory ducts, 

 been left undiscovered till now, the bare inspection of those parts in this animal 

 would instruct us: for on dividing the tunica vaginalis, rr, fig. 2, 3, I found the 

 inclosed testicle and its epididymis lying loose, insomuch that they parted from 

 each other as expressed wxy«, and with the assistance of a pretty large convex 

 glass I could see the excretory duct z, arising from one end of the testicle, 

 where the spermatic artery and vein y may be seen : after that duct has gone a 

 little way, it may be seen folded up into the body called epididymis ww, and at 

 length making the vas deferens ss. In men, and most, if not all quadrupeds, 

 the epididymides and testes adhere so close to each other, that, without some 

 dexterity in dissection, their rise from the testes is not to be discovered. The 

 vasa deferentia, ss, fig. 1, after they leave the praeparantia ab, as in men and 

 other animals, become somewhat larger; but on crossing the ureters, ee, be- 

 come less again, at their entrance into the urethra, immediately below the 

 neck of the bladder; where their orifices could be perceived on each side a 

 caruncle: nor are there any vesiculae seminales near the vasa deferentia of this 

 animal, as in boars, bulls, horses, &c. which nevertheless cannot be allowed to 

 communicate with each other as in men ; for though the vasa deferentia and 

 vesiculae seminales, of those last named animals, empty themselves into the 

 urethra at the same orifices with the vesiculae seminales, yet their communicant 

 ducts are so very short, that whatever comes by the vasa deferentia will sooner 

 escape into the urethra, than be received by the vesiculae, as in men. 



The length of the urethra, between the bladder and the penis, exceeded 4 

 inches, of which more than 3 inches and a half was inclosed with a glandulous 

 body, analogous to the prostatae in men and other animals; the orifices of the 

 secretory ducts of this glandulous body are very numerous, and open into the 

 urethra on all sides, as appeared on opening the urethra ; and compressing this 

 glandulous body, or the prostatae, its secreted liquor started out. 



This part of the urethra ikkl, fig. 2, 3, thus inclosed with the prostatae, 

 being very much contorted or folded, in its natural situation between the bladder 

 and the penis, when there is no erection, must necessarily be drawn out, and 

 become straight, when the penis is extruded on an erection ; by which means 

 this glandulous body is necessarily compressed, and the succus prostatarum 

 forced into the urethra. The prostatae of divers animals are compressed by 

 muscles framed on purpose, that inclose them, as in boars, rams, &c. but in 

 men they are compressed by the musculi levatores ani. 



At the root of the penis of the opossum we meet with 4 glandulous vesiculae 

 MMNN, two on each side, which empty themselves into the urethra, and con- 

 tain a mucous matter, like that 1 find in the glands I lately discovered in this 



