168 



THE FLUIDS. 



Origin. The blood-cells first formed in the embryo appear to 

 have their origin in the primordial cells of the germinal structure ; 

 some of these developing tissues, and others becoming isolated and 

 metamorphosed into blood -cells. These also are multiplied by 

 bipartite division (p. 126). But in the human embryo the first 

 brood of corpuscles disappears entirely by the end of the second 

 month, when the lymph and chyle begin to be poured into the 

 blood, and when they are superseded by those developed from the 

 lymph and chyle-corpuscles. (Paget.) The first blood-cells are 

 larger than the subsequent ones ; being about ^^ of an inch in 

 diameter, and nucleated. The nucleus is -g^v f an i ncn i n diame- 

 ter, central, circular, very little prominent on the surface of the cell, 



Development of first set of red corpuscles (mammalian embryo). A. Dotted nucleated and nucle- 

 olated embryo cell. B. Same with a dividing nucleus ; the division being complete at c. At D, 

 the cell also is dividing. E. Cell still containing a few granules. F. Perfect blood-corpuscle. 



Fig. 101. 



Phases of the red blood- 

 corpuscle (man), a and 6. 

 Colorless corpuscles or gran- 

 ule-cells in the coarsely and 

 the finely granular state, o 

 and d. Nucleated cells with- 

 out and with color, e. Free 

 cellaeform nucleus, or perfect 

 red corpuscle. 



and slightly granular or tuberculated. Fig. 

 100 shows the several stages of their develop- 

 ment. 



The doctrine that the continued development 

 of the red corpuscles occurs from the colorless 

 corpuscles of the blood, is the most plausible, 

 though open to some objections. Mr. Whar- 

 ton Jones has shown that in the whole animal 

 kingdom five forms of blood-corpuscle are to 

 be met with (which are represented by Fig. 

 101), viz: 1. Coarse granule-cells (a); 2. Fine 

 granule- cells (b) ; 3. Colorless nucleated cells 

 (c) ; 4. Colored nucleated cells (d) ; 5. Colored 

 n on -nucleated cells (e), or perfect red cor- 

 puscles of man and the mammalia. These 



