CAVERNOUS VESSELS. VASCULAR PLEXUSES. 



291 



to the axes of the gill laminae, and adhere to the wall of the 

 larger branchial vessels. Between the cells are roundish spaces 

 intercommunicating with one another, through which the 

 blood courses. There is no special membrane lining or limiting 

 these blood passages* 



Fig. 54. 



Fig. 54. Gill lamina of the River Crab, a, cuticula ; b, clavate cells ; 

 c, lacunar passages for the blood in the interspaces of the cells. 

 Surface view. 



Cavities similar to these, through which the blood courses, 

 are also found, according to Wilhelm Miiller, in the spleen of 

 mammals. 



* Hackel, Miiller's Archiv, 1857. Leydig, Lehrbuch, 1857, p. 385. 

 Eberth, loc. cit. 



