DESCRIPTION OF THE PLATES. 109 



be those individuals of the first class, which arc 

 about to close their existence, their nuclei hav- 

 ing disappeared ; their food, therefore, no longer 

 supplied to them, and their position in the mass 

 removed to the exterior by the eccentric deve- 

 lopement of the younger and more active neigh- 

 bouring cells. In a morbid mass of this kind, 

 as in the textures and organs of an animal gene- 

 rally, certain parts are set aside as reproducers, 

 the remaining parts performing the functions of 

 the whole mass, texture, or organ ; just as in 

 certain communities of animals certain indivi- 

 duals are set aside to reproduce the swarm, the 

 others are devoted to the duties of the hive. 



PLA.TE I. Fig. 4. Two portions of the primary or germinal membrane 

 from the tubes of the tubular portion of the hu- 

 man kidney. The germinal spots of the gland 

 are seen imbedded in the substance of the mem- 

 brane. The external layer of this membrane, 

 which may occasionally be seen with the nuclei 

 detached from it, is the basement or homege- 

 neous membrane of Mr. Bowman. In other in- 

 stances, as when the epithelia are but slightly 

 developed, it becomes difficult to decide whether 

 we have merely the germinal membrane, or both 

 the membrane and its epithelia before us. 



INTESTINAL VILLI. 



PLATE I. Fig. 5. Extremity of a villus immediately before absorption 

 of chyle has commenced. It has cast off its pro- 

 tective epithelium, and displays, when com- 

 pressed, a network of peripheral lacteals. The 

 granular germs of the absorbing vesicles, as yet 

 undeveloped, are seen under its primary mem- 

 brane. 



