CH. xxvi.J DEVELOPMENT OF BLOOD-CORPUSCLES. 



425 



filled with fluid (fig. 357); by the extension of the cavity of the 

 cells into their processes anastomosing 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 cir- 

 culation. This method of 

 formation is called intracel- 

 liil'tr. 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 per- 

 formed. 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 

 coloured corpuscles undergo 

 disintegration in the spleen ; 

 and indeed corpuscles in vari- 

 ous degrees of degeneration 

 have been observed in that 

 organ. 



Fig. 357. Further development of blood-cor- 

 puscles in connective tissue cells and .trans- 

 formation of the latter into capillary blood- 

 vessels, a, an elongated cell with a cavity in 

 the protoplasm occupied by fluid and by blood- 

 corpuscles which are still globular ; b, a hol- 

 low cell, the nucleus of which has multiplied. 

 The n<;w nuclei are arranged around the 

 wall of the cavity, the corpuscles in which 

 have now become discoid ; c, shows the mode 

 of union of a " heemapoietic " cell, which, 

 in this instance, contains only one corpuscle, 

 with the prolongation (bl) of a previously 

 existing vessel ; a and c, from the new-born 

 rat ; b, from the foetal sheep. (E. A. Schaf er.) 



Origin of the White 

 Corpuscles. The hyaline corpuscles are derived from the 

 lymphocytes which are formed in the lymphatic glands, and 

 enter the blood-stream by the thoracic duct. 



Fig. 358. Coloured nucleated corpuscles, from the red marrow of the guinea-pig. 

 (. A. Schafer.) 



The finely granular leucocytes which are the most numerous 

 white corpuscles in the blood originate either in the same way, or 

 by cell division in the blood-stream itself. 



The coarsely granular eosinophile corpuscles, which form about 

 5 per cent, of the total leucocytes in normal blood, are found in 

 larger numbers in the connective tissue in various parts of the 



