Resolution of the formed elements 83 



the haemoglobin. The membrane and nucleus of the red blood 

 corpuscles persist longer but they also are ultimately digested. The 

 excretion of haemoglobin from the phagocytes, just mentioned in the 

 case of the macrophages of the guinea-pig, is also observed in the 

 Actinians, whose coelenteric cavity is tinted by a rose-coloured solution. 



We have seen that in the Actinians intracellular digestion takes [89] 

 place in a distinctly acid medium, whilst in the intestinal cells of the 

 Planarians it takes place in one that is only weakly acid. The 

 macrophages of the guinea-pig, during the resorption of red blood 

 corpuscles of the goose, carry on the digestive process in a medium 

 which shows a still weaker acidity. When made to ingest granules of 

 blue litmus there is no change of colour. Nor does alizarin sulpho- 

 acid give any reaction, probably owing to the fact that it exerts a 

 toxic action on the protoplasm of the macrophages. If, however, we 

 add to a drop of the peritoneal exudation of a guinea-pig, containing 

 macrophages filled with red blood corpuscles of the goose, a little of 

 Ehrlich's 1 % solution of neutral red, the red brick tint at once makes 

 its appearance in the content of these phagocytes. This coloration 

 is identical with that described in the Amoebae which digest Bacteria 

 or in the intestinal phagocytes of the Planarians. It may, then, be 

 regarded as an indication of weak acidity. This coloration is main- 

 tained for some hours, after which it gives place to complete decolora- 

 tion, a phenomenon that must be attributed, as in many other cases, 

 to the neutralisation of the acid by the alkaline protoplasm that has 

 been macerated in the fluid after the death of the macrophages. 



The example we have chosen the destruction of red blood 

 corpuscles of the goose by the macrophages of the guinea-pig- 

 may serve as a prototype of the resorption of formed elements in 

 general. If, instead of red blood corpuscles of the goose, we inject 

 into the guinea-pig's peritoneal cavity pigeon's or fowl's blood, the 

 essential phenomena will be the same. The red blood corpuscles will 

 always induce positive chemiotaxis, especially of the macrophages, 

 which in turn will ingest the nucleated red corpuscles. It may be 

 that in certain cases, when fowl's blood containing red corpuscles 

 that are not very resistant is injected, a certain number of the cor- 

 puscles immediately undergo a partial solution in the peritoneal fluid 1 . 



1 Krtmpecher (Centralbl. f. Bakteriol. u. Parasitenk., l te Abt., Jena, 1900, 

 Bd. xxvin, S. 588) has obtained a serum which was even capable of altering the 

 nuclei of the red corpuscles of the frog. These nuclei must be much less resistant 

 than those of the red blood corpuscles of birds, such as the goose, fowl and pigeon. 



62 



