FORMATION OF RED BLOOD CORPUSCLES. 729 



SANGUIFICATION. 



The occurrence of this process in the economy of the higher animals 

 and of Man, is implied in the proper expression of making blood. The 

 corpuscles, both red and white, waste, or become worn out, from the 

 nutritive changes which occur in the solid tissues, and in the blood 

 itself. Their number, especially that of the red ones, certainly in- 

 creases with a high rate of living, and materially diminishes from 

 hemorrhage, starvation, or disease. This waste, and loss of number 

 in the corpuscles, must be repaired. 



The white corpuscles are supposed to be derived from the lymph and 

 chyle corpuscles which enter the blood, and are identical with its white 

 corpuscles, in size, form, structure, and chemical composition. The 

 large number of white corpuscles found in the blood, three or four 

 hours after complete digestion, their greater abundance in the veins 

 than in the arteries, and especially in the left innominate vein as com- 

 pared with other veins in the body, are facts which favor this view. 

 No other ordinary source for the production of the white corpuscles of 

 the blood has been suggested, although it has been supposed that, 

 under certain circumstances, as in local inflammation or excitement, 

 they might possibly arise within the capillaries, by subdivision and 

 growth of the nuclei in the walls of those vessels, and then, becoming 

 detached, be moved on with the blood. Some may also arise within 

 the spleen. 



The mode of formation of the blood corpuscles, both white and col- 

 ored, in the embryo and its membranes, is peculiar, and will be de- 

 scribed in the Section on Development. After birth, the red corpuscles, 

 it is generally believed, are developed from the white ones, however 

 these latter may arise. Many transitional forms have been traced in 

 the blood. In the progress of change in the Mammal, as described 

 by some (Funke, Paget, Kolliker), the contents of the white corpus- 

 cle become more fluid and homogeneous, the compound nucleus dis- 

 appears, the surface becomes smooth, the size diminished, the shape 

 flattened, disc-like and then biconcave, an exceedingly thin envelope 

 forms around them, and they acquire a red color in their interior. 

 According to others (Wharton Jones, Busk, Huxley), this is true, as re- 



firds the nucleated colored corpuscles of Birds, Reptiles, Amphibia, and 

 ishes ; but in the Mammalian non-nucleated colored corpuscle, it is 

 the nuclear portion, only, of the white corpuscle which is converted, 

 by the necessary changes, into a red corpuscle. By some, it is thought 

 that the smaller white corpuscles, or the larger ones after subdivision, 

 undergo this transformation by flattening, disappearance of the nucleus, 

 and acquisition of cruorin; others regard the smaller pale bodies, 

 often described in the blood, as if they were wasting, not growing, red 

 corpuscles. 



In the Oviparous Yertebrata, therefore, the red-blooded corpuscle is a trans- 

 formed pale corpuscle; but in the Viviparous mammalia, including Man, the 

 red corpuscle is the homologue of the nucleus only of the Oviparous blood 

 corpuscle. In both cases, the pale corpuscle is perhaps a naked cell or gym- 



