170 THE FLUIDS. 



acquire a pale tinge of blood color, and this always coincides with 

 the softening of the shadows which before made them look nebu- 

 lous, and with the final vanishing of all the granules, with the ex- 

 ception sometimes of one, which remains some time longer like a 

 shining particle in the corpuscle, and has probably been often mis- 

 taken for a nucleus (E). The blood color now deepens, and at the 

 same rate the corpuscles become smooth and uniform; biconcave, 

 having previously changed the nearly spherical form for a lenticular 

 or flattened one ; smaller, apparently by condensation of their sub- 

 stance, for at the same time they become less amenable to the influ- 

 ence of water ; more liable to corrugation and to collect in clusters ; 

 and heavier, so that the smallest and fullest colored corpuscles 

 always lie deepest in the field (F). Thus the most developed state 

 of the mammalian red corpuscles appears to be that in which they 

 are full-colored, circular, biconcave, small, uniform, and heavy. This 

 is the state in which they appear to live the longer and the most 

 active part of their lives." 1 



It will be observed that Mr. Paget regards the mature blood- cor- 

 puscles not as mere free nuclei, as some observers have done (p. 115), 

 but as non-nucleated cells. The blood-cells of the amphibia are, 

 however, always nucleated. 



The idea maintained by "Weber and others, that the liver is the 

 special agent in the development of the blood-cells in the embryo, 

 appears to be applicable to oviparous animals, but not to the mam- 

 malia. The fact, however, that the blood of the hepatic vein in 

 man contains a much greater amount of blood-cells than does that 

 of the vena portae, indicates that they are developed with peculiar 

 activity in that organ. This, however, may be a mere consequence 

 of the fact that the blood of this vein is also rich in colorless cor- 

 puscles, and which undergo their development while in the hepatic 

 vessels, independently of any peculiar action of the liver itself. 



Thus the life of the blood is seen to inhere in the red corpuscles, 

 the colorless corpuscles, and the fibrine (pp. 158 and 161). 



Function. The view which ascribes to the red corpuscles the 

 function of absorbing oxygen while in the lungs, and giving it par- 

 tially off in the capillaries, while they also absorb carbonic acid in 

 the capillaries, and give it off in the air expired from the lungs, 



1 The necessity of fatty elements in aid of the development of the blood-cells is 

 inferred from their composition, already stated. Hence, also, their rapid formation 

 from the use of cod-liver oil, as observed by Popp. 



