144 THE CELL 



importance, and undergo fatty degeneration. Thus, during the 

 metamorphosis of Echinoderm larva? and of Nemertines, certain 

 portions disappear ; and, similarly, the young Frog during its 

 development loses its conspicuous tail, which acted as a rudder. 

 In all these cases the cells of these degenerating- organs undergo 

 a fatty metamorphosis, die and disintegrate. In the meantime a 

 large number of migratory cells or phagocytes have collected in 

 their neighbourhood, and these commence to devour and digest 

 the degenerated tissue, as can be plainly seen during life in trans- 

 parent marine animals. 



Secondly, just as during the normal processes of development, 

 the phagocytes occupy themselves in reabsorbing particles, the 

 death or disintegration of which has been brought about either by 

 normal or pathological conditions. Red blood corpuscles become 

 destroyed after they have circulated in the blood for a certain 

 time. In splenic blood their remains have been seen in the bodies 

 of white corpuscles, which here again fulfil their function of 

 getting rid of dead material. When in consequence of a wound 

 an effusion of blood occurs in the tissue, and thousands of blood 

 corpuscles and elementary particles are destroyed, the migratory 

 cells again set to work, and produce reabsorption and healing. 



Thirdly, and lastly, the phagocytes during infectious diseases 

 constitute a body-guard to the organism, in opposing the spread 

 of the micro-organisms in the blood and tissues. 



Metchnikoff has rendered great service in drawing attention to 

 this circumstance (V. 13-15, IV. 22). He succeeded in showing 

 that the Cocci of erysipelas, the Spirilla of relapsing fever, and the 

 Bacilli of anthrax were eaten up by the wandering cells, and thus 

 rendered harmless (Fig. 61). The micro-organisms, of which as 

 many as from ten to twenty may be present in one cell, after a 

 certain time show distinct signs of degeneration. If the micro- 

 organisms are present in the blood, they are destroyed, especially 

 in the spleen, liver, and red bone marrow. If they succeed in 

 settling down in some place in the tissue, the body endeavours to 

 get rid of the intruders by collecting as the result of inflammatory 

 processes a large number of migratory cells to the spot. 



As Metchnikoff expresses it, between micro-organisms and 

 phagocytes an active war is raging. This is settled in favour of 

 one or other party, resulting, as the case may be, in the recovery 

 or death of the affected animal. 



The power possessed by migratory cells of destroying certain 



