MINUTE ANATOMY OF THE CAPILLARIES. 279 



internal membrane covers only the convex surface of the valves. 

 The proper substance of the valve is composed of finely fibril- 

 lated connective tissue with stellate and fusiform cells. 



The muscular fibres which have been described by Wahlgren 

 in the larger valves, I have not been able to discover with 

 certainty. 



The sacciform transparent appendages of the veins on the 

 cardiac side of the valves of the veins (to be found in the axillary 

 external and internal jugular and crural veins, as well as in the 

 other branches), which, according to Remak,* consist exclusively 

 of bundles of smooth muscular fibres, I find are not contractile. 



CAPILLARIES. 



Capillary vessels removed from living adult animals, and 

 examined with due precaution, as, for example, those of the hya- 

 loid membrane of Frogs, treated with the fluid of the aqueous, 

 appear to be composed of a delicate, double-contoured, dull 

 membrane, in which oval nuclei are imbedded at tolerably 

 regular intervals. The parietes of these tubes are therefore 

 not structureless. The capillaries of the hyaloid of the Frog 

 appear to consist of a soft cloudy substance which in no respect 

 differs from the substance of the delicate threads of protoplasm 

 given off by the cells of the tunica adventitia. In young 

 living animals, as in tadpoles, we may still more easily convince 

 ourselves that the capillary wall is not completely structureless, 

 but that granules are distributed through it in a stellate 

 manner, and that in its general appearance it closely resembles 

 protoplasm. The wall here frequently appears uneven and 

 provided with small teeth, or prolonged into fine partly solid 

 and partly hollow funnel-like and, for the most part, non- 

 nucleated pointed processes. The substance of these is always 

 more granular than that of the rest of the membrane. 



Such lateral processes are found also in adult animals, 

 Strieker)- having seen them in the nictitating membrane of the 



* Uber contractile Klappensdcke an den Venen des Menschen, Deutsche 

 Klinik, iii., p. 32, 1856. 



\ Sitzunysberichte der Wiener Akademie, Band xii. 



