428 THE BLOOD [CH. XXVI. 



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 wholly made out. A certain number of the 

 coloured corpuscles undergo disintegration in the liver and spleen ; 

 corpuscles in various degrees of degeneration have been observed in 

 the latter organ. 



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. 



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. Most observers consider they 

 arise in the red marrow. 



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 body ; they 

 are found in special abundance in red marrow, in which at one time 

 they were supposed to originate. Most look upon each eosinophile 

 corpuscle as a little unicellular gland, and the mass of corpuscles as 

 a migratory glandular tissue. 



Chemistry of the Blood-Corpuscles. 



The white blood-corpuscles. Our chemical knowledge of the 

 white corpuscles is small. Their nucleus consists of nuclein, their 

 cell protoplasm yields proteids belonging to the globulin and nucleo- 

 proteid groups. The nucleo-proteid obtained from them is not quite 

 the same thing as fibrin-ferment (thromliri) ; it is probably the zymogen 

 or precursor of the ferment (protlirombiri) ; the action of the calcium 

 salts of the plasma in shed blood is to convert prothrombin into 

 thrombin (see p. 414). The protoplasm of these cells often contains 

 small quantities of fat and glycogen. 



The red blood-corpuscles. 1000 parts of red corpuscles con- 

 tain : 



Water 688 parts. 



o_ H ... /Organic 303 '88 



Sollds (inorganic S'12 



One hundred parts of the dry organic matter contain 



Proteid 5 to 12 parts. 



Haemoglobin 86 to 94 ,, 



Lecithin 1-8 



Cholesterin O'l 



The proteid present is identical with the nucleo-proteid of white 

 corpuscles. The mineral matter consists chiefly of chlorides of 



