STRUCTURE OF THE TUBULI SEMINIFERI. 135 



There are still some differences of opinion with regard to 

 the nature of the membranous walls. According to the older 

 statements of Henle,* which, as he himself in a later published 

 workf supposes, were founded on examinations of the smaller 

 Mammalia, it is hyaline and structureless, with a few elongated 

 oval nuclei. Lereboullet,J describing them in the Rabbit, 

 likewise terms them structureless. Valentin considers that 

 a middle muscular layer can be demonstrated, lined internally 

 by a layer of pavement epithelium, and covered externally by 

 a perfectly clear and transparent membrane, containing elon- 

 gated cell nuclei. Gerlach || finds that differences occur in the 

 structure of the tubules in newly born and young animals, on 

 the one hand, and adults on the other. In the former the 



Fig. 167. 



Fig. 167. Tubuli seminiferi of a year-old Child with csecal ex- 

 tremities. 



walls consist of a perfectly transparent structureless membrane, 

 with a variable number of elongated cell nuclei ; in the latter 

 there is an external fibrous layer of connective tissue, with 

 scattered elongated oval nuclei. Henlelf gives the following 

 description of the membrane of the tubuli seminiferi : " In 

 longitudinal sections of the tubules it appears longitudinally, 

 in transverse, concentrically striated; in both aspects, dark 

 rod-shaped nuclei appear between the strise ; when spread out 

 and examined from the surface, it is homogeneous, with 



* AllgemeineAnatomie, p. 926. 



t Handbuch der Eingeweidelehre, p. 354. 



I N. A. Acad. Nat. Cur., Yol. xxiii., p. 10. 



Handworterbuch der Physiologic, v. R. Wagner, Band i., p. 785. 



|| Handbuch der Gewebelehre, p. 367. 



IT Handbuch der Eingeweidekhre, p. 353. 



