THE CIRCULATING LIQUIDS OF THE BODY 33 



in which red corpuscles are actually destroyed.* Destruc- 

 tion of the corpuscles also seems to take place in the spleen 

 and bone-marrow. Although the statement that free blood- 

 pigment exists in the plasma of the splenic vein is incorrect, 

 red corpuscles have been seen in various stages of decom- 

 position within large amoeboid cells in the splenic pulp ; and 

 deposits containing iron have been found there and in the 

 red bone-marrow in certain pathological conditions. It is 

 not unlikely that the coloured corpuscles may break up also 

 in other localities, and even to some extent in the blood itself. 



The lymphocytes are undoubtedly, the coarsely granular 

 oxyphile cells probably, and the hyaline cells possibly, derived 

 from the lymph. The lymphocytes are probably identical 

 with the small lymph-corpuscles, and have little, if any, 

 power of amoeboid movement. They are formed largely in 

 the lymphatic glands, for the lymph coming to the glands is 

 much poorer in corpuscles than that which leaves them. 

 The lymphatic glands, however, are not the only seat of 

 formation of leucocytes, for lymph contains some corpuscles 

 before it has passed through any gland ; and although a certain 

 number of these may have found their way by diapedesis 

 from the blood, others are formed in the diffuse adenoid 

 tissue, or in special collections of it, such as the tonsils, the 

 Peyer's patches and solitary follicles of the intestine, and 

 the splenic corpuscles. To a very small extent white blood- 

 corpuscles may multiply by karyokinesis in the blood. 



The fate of the leucocytes is even less known than that 

 of the red corpuscles, for they contain no characteristic 

 substance, like the blood-pigment, by which their destruction 

 may be traced. That they are constantly breaking down is 

 certain, for they are constantly being produced. But we do 

 not know whether, under normal conditions, this process 

 takes place exclusively in the blood-plasma or in particular 

 organs or tissues. 



* Although it cannot be doubted that in all animals whose blood 

 contains haemoglobin the iron found in the liver bears an important 

 relation to the building up or breaking down of the blood-pigment, the 

 injection of haemoglobin or haemin, indeed, increasing markedly the 

 amount of iron in the liver, as well as in the spleen, bone -marrow and 

 other tissues, this does not seem to be the only function of the hepatic 

 Iron, for the liver of the crayfish and the lobster, which have colourless 

 blood, is rich in iron. 



