10 PHILOSOPHICAL TKANSACTIONS. [aNNO 1750. 



plicae or folds, connected together by cellular membrane. This was rightly 

 seen by De Graaf, de Part. Genital. Viror. p. 65. 



In the upper part of the epididymis, which he calls the head, and which is 

 firmly attached to the tunica albuginea, the structure is different. For there 

 this single canal is divided into 10, 12, or more, canals. These Prof. H. calls 

 vasa efFerentia semen. 



Folded up, and collected into a cone, each forms a distinct fasciculus, and by 

 a retrograde duct returns towards the lower part of the testicle, and enters into 

 the middle of it, at the place where the epididymis, loose on one side, adheres 

 only on the other. De Graaf has given a pretty good delineation of these ves- 

 sels and cones. These vessels are gradually extended on the surface of the tes- 

 ticle, which is continuous with the albuginea, and running parallel and con- 

 joined,* they form a net (rete). 



From this conj unction -^ it often happens that when only 1 or 2 of the vasa 

 efferentia are injected from the epididymis, all of them become filled. De Graaf 

 alone saw and delineated this structure ; but he has represented the vessels too 

 parallel, and not joined together by intermediate branches. He has also made 

 them too long. All other anatomists have taken them either for a single duct, 

 or for a blind membrane. 



From the rete or net are sent forth vessels without plicae or folds, and which 

 from their straight direction, Prof. H. terms recta vascula testis. They are 

 larger than might be supposed, and more tender than the canal of the epididymis, 

 so as to be easily burst by the weight of the quicksilver. Into these straight 

 vessels (recta vascula) are inserted the yellowish serpentine vessels of the testicle, 

 which Ruysch so beautifully resolved into hair-like filaments. It has some 

 times happened that the quicksilver has entered even these exceedingly mi- 

 nute and tender vessels, so as to place it beyond all doubt that they are hollow 

 canals. 



Thus it appears that the yellowish-coloured semen is generated in the serpen- 

 tine vessels (vascula serpentina) ; that it passes from thence into the straight 

 vessels, (vasa recta) ; that by the straight vessels it is conveyed into the rete or 

 net ; and that from the rete or net it is carried through the tortuous vascula ef- 

 ferentia into the epididymis. + 



From the epididymis the passage of the semen is two-fold, one by no means 

 obvious, the other well known, and leading to the vesiculae. The first of these 



* By intermediate branches. t Connexion by intermediate branches. 



J The structure of the testicles in man, and other animals, was afterwards farther illustrated by the 

 present professor of anatomy at Edinburgh, Dr. Monro, in his inaugural thesis De Testibus et Se- 

 niine in Variis Animalibus, published in 1755. 



