THE BLOOD. 93 



in the following way. Small globules, of varying size, of coloring 

 matter arise in the protoplasm of the cells, and the cells Uiemselves be- 

 come branched, their branches joining tbe branches of similar cells. 

 The cells next become vacuolated, and the red globules are free in a 

 cavity filled with fluid (Fig. 85) ; by the extension of the cavity of the 

 cells into their processes anastomosing vessels are produced, which ulti- 

 mately 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 intra- 

 cellular (Schafer). 



(2.) From the ivliitc, 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 cor- 

 puscle, 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. 



(3.) From the medulla of hones. Colored 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. 83, 84). These cells become 

 colored from the formation of hgemoglobin 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 protoplasm may grow up again and form a number of red corpuscles 

 in a similar way. 



(4.) From the tissue of the spleen. It is probable that colored as well 

 as colorless corpuscles may be produced in the spleen. 



(5.) From Microcytes. Hayem describes the small particles (micro- 

 cytes), previously mentioned as contained in the blood (p. 71), and which 

 he calls haematoblasts, as the precursors of the red corpuscles. They ac- 

 quire color, and enlarge to the normal size of red corpuscles. 



Without doubt, the red corpuscles have, like all other parts of the 

 organism, a tolerably definite term of existence, and in a like manner 

 die and waste away when the portion of work allotted to them has been 

 performed. Neither the length of their life, however, nor the fashion 

 of their decay has been yet clearly made out. It is generally believed 

 that a certain number of the colored corpuscles undergo disintegration 

 in the spleen ; and indeed corpuscles in various degrees of degeneration 

 have been observed in that organ. 



Origin of the Colorless Corpuscles. The colorless corpuscles of 

 the blood are derived from the lymph corpuscles, being, indeed, indis- 

 tinguishable from them ; and these come chiefly from the lymphatic 

 glands. Their number is increased by division. 



