TUBULI SEMIN1FERI. 149 



straight : it then takes the name of Vas Deferens, and con- 

 tinues on the back of the testicle and at the inner side of the 

 epididymis to the spermatic cord.*f 



A small solitary vessel or duct, has been observed by Haller, 

 Monro, and several other anatomists, to proceed from near the 

 upper part of the epididymis : sometimes it unites to the epi- 

 didymis below, and somejtimes it proceeds upwards. The nature 

 of this vessel has not been ascertained with certainty. 

 This duct or appendix which was named vasculum aberrans 

 by Haller, discharges mucus into the vas deferens. Occasion- 

 ally two or three are met with, all of which commence, by a 

 cul de sac, or coecal extremity. 



Monro and Lauth, have both endeavored to estimate the 

 length of the seminiferous ducts. This, however, could not be 

 done directly, in consequence of the fragility of the ducts. 

 Their estimate is founded partly on measurement, and partly on 

 calculation, and can only be considered an approximation to the 

 truth. The estimate of Monro exceeds that of Lauth. Accord- 

 ing to the former, there are three hundred lobules, each one con- 

 sisting of a single seminiferous duct, arranged in the lobules in 

 a series of close serpentine doublings, which are held together 

 by some delicate cellular tissue. When this cellular tissue is 

 destroyed by maceration, for a short time, each duct may be 

 drawn out with ease, and resembles the unraveled thread of a 



* De Graff appears to have been the first anatomist who made much pro- 

 gress in the successful investigation of the structure of the testicle ; and Haller 

 ought to be mentioned next to him, on account of the plate exhibiting this 

 structure, and the explanation of it, which he published in the Philosophical 

 Transactions of London, for 1749. This plate has been republished by the 

 second Monro, in the Literary and Physical Essays of Edinburgh, and also in 

 his Inaugural Thesis. Haller has likewise republished it in his Opera Minora. 

 It represents not only the vasa efferentia, and the cones formed by their convo- 

 lutions, but also the rete testis, and the vasa recta. Haller could inject no 

 farther than this ; but Monro and Hunter soon after succeeded so as to fill a 

 considerable portion of the body of the testicle with mercury, injected by the 

 vas deferens. 



f In Mr. Charles Bell's Anatomical Collection in London, there is a prepara- 

 tion by his assistant, Mr. Shaw, in which the tubuli testis are completely 

 injected with quicksilver and unraveled. I saw also in Leyden, one nearly as 

 successfully executed by Professor Sandifort. H. 



13* 



