STRUCTURE OF THE TUBULI SEMINIFERI. 137 



The tubuli seminiferi of the embryo of a Cow, eight inches 

 in length, as well as those of a Calf, examined in the fresh 

 state, exhibit a tolerably thick structureless inembrana propria, 

 and a tolerably thick nucleated adventitia. 



In the Dog, Guinea-pig, and Rabbit I have also been able to 

 distinguish two tunics. 



On the other hand, in the tubuli seminiferi of the adult Man 

 I can only discover the single membrane which has been so 

 completely and accurately described by Henle. 



Peculiar cell masses, first noticed by Kolliker,* are found 

 imbedded in the interstitial connective tissue between the 

 tubuli seminiferi, and are to be accounted as indifferent cells 

 of the connective tissue. f 



LeydigJ also holds the same opinion, maintaining it to be 

 a fact of general application for the testes of all Mammals, that 

 the connective tissue uniting together the seminiferous tubules 

 contains also a cellular mass, which, though only present in 



Fig. 169. 



Fig. 169. Portion of a seminiferous tubule from the Calf, a, Ad- 

 ventitia ; 6, propria. 



small quantity, follows the course of the bloodvessels, and 

 everywhere surrounds the seminiferous tubules, where it is 

 developed to a considerable extent. In the Boar it undergoes 

 so remarkable a development that a section of the testis 

 presents a chocolate colour ; and the same occurs in the Horse. 

 A similar material is also found in the Lizard. 



* Mikroskop. Anatomic, Band ii., p. 392. 

 t Handbuch der Gewebelehre, p. 524. 

 J Lehrbuch der Histologie, p. 594. 



