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HAND-BOOK OF PHYSIOLOGY. 



vacuolated, and the red globules are free in a cavity filled with fluid (Fig. 

 88) ; by the extension of the cavity of the cells into their processes anas- 

 tomosing vessels are produced, which ultimately join with the previously 

 existing vessels,, and the globules, now having the size and appearance of 

 the ordinary red corpuscles, are passed into the general circulation. This 

 method of formation is called intracellular (Schafer). 



FIG. 88. Further development of blood-corpuscles in connective-tissue cells and transformation 

 of the latter into capillary blood-vessels, a, an elongated cell with a cavity in the protoplasm occu- 

 pied by fluid and by blood-corpuscles which are still globular; ft, a hollow cell, the nucleus of which 

 has multiplied. The new nuclei are arranged around the wall of the cavity, the, corpuscles in which 

 have now become discord; c, shows the mode of union of a "hsemapoietic 11 cell, which, in this in- 

 stance, contains only one corpuscle, with the prolongation ( bl ) of a previously existing vessel ; a and 

 c, from the new-born rat; 6, from the foetal sheep. (E. A. Schafer.) 



(2.) From the white corpuscles. The belief that the red corpuscles are 

 derived from the white is still very general, although no new evidence 

 has been recently advanced in favor of this view. It is, however, uncer- 

 tain whether the nucleus of the white corpuscle becomes the red corpus- 

 cle, or whether the whole white corpuscle is bodily converted into the red 

 by the gradual clearing up of its contents with a disappearance of the 

 nucleus. Probably the latter view is the correct one. 



FIG. 89. Colored nucleated corpuscles, from the red marrow of the guinea-pig. (E. A. Schafer.) 



(3.) From the medulla of bones. Red corpuscles are to a very large 

 extent derived during adult life from the large pale cells in the red mar- 

 row of bones, especially of the ribs (Figs. 44, 89). These cells become 

 colored from the formation of haemoglobin chiefly in one part of their 

 protoplasm. This colored part becomes separated from the rest of the 

 cell and forms a red corpuscle, being at first cup-shaped, but soon taking on 

 the normal appearance of the mature corpuscle. It is supposed that the 





