60 THE HUMAN .BOD Y. 



cess of alteration or removal, and formation; their number 

 is largely increased by taking food, even more than that of 

 the red, so that their proportion to the red rises, from 1 

 to 1000 during fasting, to 1 to 250 or 300 after a meal. 

 They no doubt multiply to a certain extent by division 

 while circulating in the blood, but the majority come from 

 the lymphatic glands and similar structures (see Chap. 

 XXII.) found in many parts of the Body, which con- 

 tain many cells like pale blood corpuscles, and often in 

 process of division. From these organs the corpuscles en- 

 ter the lymph-vessels and are carried on into the blood. 

 From the capillary blood-vessels many again migrate, and 

 it is probable that these emigrants take part frequently in 

 the repair or regeneration of injured tissues. Being un- 

 differeiitiated and specialized to no line of work they are 

 ready to take up any that comes to hand, and may be com- 

 pared to the young men in a community who have not yet 

 selected an occupation and are on the lookout for an open- 

 ing. It is asserted by some authorities that many white 

 corpuscles are transformed into red, but this is open to 

 doubt. The corpuscles of nearly all invertebrate anfmals 

 are colorless only, although the blood plasma of some con- 

 tains haemoglobin in solution. Amphioxus, the lowest 

 undoubted vertebrate animal (see Zoology), possesses onl} 

 colorless corpuscles in its blood. Higher and more com- 

 plex animals need more oxygen, and as blood plasma dis- 

 solves very little of that gas, they develop in addition the 

 haemoglobin-containing corpuscles which pick it up in the 

 gills or lungs and carry it to all parts of the Body, leaving 

 it where wanted (see Chap. XXV.). In cold-blooded 

 vertebrates the red corpuscles are not nearly so many in 

 proportion as in the warm-blooded, which use far more 

 oxygen. The older view was that the mammalian red cor- 

 puscle represented the nucleus of one of the white,- in which 

 haemoglobin had been formed and from about which the 

 rest of the corpuscle had disappeared. This, however, does 

 not seem to be the case. In adults new red blood corpus- 

 cles seem to be formed by the segregation of portions of the 

 protoplasm of peculiar cells found in various parts of the 



