BLOOD-FORMATION. 93 



walls, the effects are always evil, and often fatal. In 

 ordinary nutrition and secretion, the living matter im- 

 bedded in each tissue or organ, selects certain con- 

 stituents, and the fluid deprived of these is again 

 taken back into the circulation. The important part 

 played by the bioplasts of the capillaries in these pro- 

 cesses is thus stated by Dr. Beale : 



" I believe that the bioplasts of the capillary vessels play a 

 far more important part in the changes of the body than has 

 hitherto been supposed. They are as intimately concerned in 

 the process of secretion and excretion as they are in the selec- 

 tion, preparation, and distribution of nutrient constituents. The 

 bioplasts of the capillaries, of the lungs are the agents by which 

 certain animal matters are separated from the blood and trans- 

 ferred to the air in the pulmonary air cells, and it is probable 

 they are also concerned in facilitating the changes which take 

 place between the gaseous constituents of the air and blood. 

 In connection with the capillaries of all secreting organs the 

 bioplasts are numerous, and they select and remove certain 

 substances from the blood and transfer them in an altered form 

 to the secreting cells of the gland. They are in great number 

 upon the vessels of the villi of the small intestines, in some 

 cases being so very close together as to leave little membranous 

 structure between them. These bioplasts of the intestinal 

 capillaries receive the nutrient substances after they have been 

 already once modified by the bioplasm of the epithelial cells of 

 the villi, and transmit them in an altered form to the interior 

 of the capillary, where many of their constituents are at once 

 taken up by the bioplasts (white blood corpuscles and minute 

 particles of bioplasm) in the blood itself." 



These remarks entirely harmonize with the views of 

 many of the older physiologists on the importance of 

 the parenchymatous or capillary tissue which to them 

 was the ultimate anatomical element and more espe- 

 cially with those of Fletcher, who placed all the vital 



