72 Chapter IV 



their contents. In tliie intestinal phagocytes of the Planarian, as in 

 the phagocytes of the blood (leucocytes) of the snail and "ver blanc/' 

 the haemoglobin diffuses through the wall of the red corpuscle, 

 whose most resistant parts are the nucleus and the membrane. These 

 resistant residual fragments, impregnated with haemoglobin, become 

 brown in the Planarian, in the "ver blanc," and also, but in a less 

 degree, in the snail. The most appreciable difference consists in 

 the formation of excretory vacuoles, containing concretions, in the 

 Planarian, and the absence of these vacuoles in the blood phagocytes 

 of the other Invertebrata. We have, however, less right to attribute 

 a fundamental importance to this difference, in that the phenomena in 

 the Actinians, which ingest the red blood corpuscles by the amoeboid 

 cells of their entoderm, are in all respects (with the exception of the 

 presence of these special excretory vacuoles) comparable to the 

 phenomena observed in the Planarians. From the fact that in these 

 two examples we have to do with a true intracellular digestion, it 

 must be admitted that the modifications of the red blood corpuscles 

 within the phagocytes of the blood in the snail and in the larva of the 

 cockchafer, must also be placed in the same category of phenomena. 



In order to make a more thorough study of this intracellular 

 digestion in the phagocytes of the blood, we must direct our attention 

 to larger and more highly organised animals than the snail and the 

 "ver blanc." Let us take, first, an example among the inferior 

 cold-blooded Yertebrata. The red blood corpuscles of a few drops 

 (0*25 C.C.) of the blood of a guinea-pig injected into the peritoneal cavity 

 of a gold-fish (Cyprinus auratus) are not appreciably changed by the 

 peritoneal fluid itself ; but the numerous leucocytes that are found in 

 [78] the peritoneal fluid seize them and ingest them, just as do the phago- 

 cytes of the blood of Invertebrata, or the intestinal phagocytes in the 

 Planarians and Actinians in the case of the red blood corpuscles of 

 the goose. Each leucocyte of the Cyprinus ingests several red blood 

 corpuscles and subjects them to intracellular digestion. The stroma 

 of the red corpuscles becomes permeable ; the haemoglobin diffuses 

 into the nutritive vacuoles and at the end of a shorter or longer period 

 the whole is dissolved and decolorised (Fig. 16). Here no brown 

 pigment is produced and the red corpuscles are completely digested, 

 leaving no " remains"; in this respect differing fi'om the process in the 

 Invertebrata mentioned. 



This result depends, probably, partly upon the more feeble resist- 

 ance offered by the non-nucleated red corpuscles of Mammals, and 



