364 SUMMARY OF CURRENT RESEARCHES RELATING TO 



other words, in most tliougli not in all cases we find that when meso- 

 derm cells are confronted with a large mass of food-material which 

 they cannot devour singly, they fuse into a plasmodium, which eats up 

 the whole available food. Not only blood but milk also is absorbed 

 by mesodermal cells, and further these cells appear to have some 

 means of distinguishing between desirable and undesirable substances. 

 The property of ingestion is not confined to the lower forms, for Koch 

 has observed both Bacillus anthracis and the bacillus of septicaemia 

 inclosed in white blood-corpuscles ; the power of intracellular 

 ingestion is, in other terms, used as a protection against harmful bodies 

 which come to an organism from without. Septic organisms, then, 

 must be a very old source of trouble, and some arrangements, snch as 

 the peculiar test of Ascidians or the nematocalyces of Plumularia, 

 may owe their origin to their influence. 



Metschnikoff hopes that the advances lately made by pathology 

 will benefit zoology, which, in its turn, will help to form a compara- 

 tive pathology based on the doctrine of evolution. 



In a further communication* E. Metschnikoff discusses the ances- 

 tral history of the inflammatory process. He has lately applied the 

 name of phagocytes to certain cells which have the power of ingesting 

 and sometimes of absorbing food-particles ; the intracellular absorp- 

 tion which goes on in the mesoderm of the Tnvertebrata, is found to 

 obtain also in that of the Vertebrata. The tail of the Batrachia, 

 during the early stages of its absorption, contains a number of cells, 

 which, when left undisturbed, throw out fine radiating pseudopodia ; 

 these contained remnants of nerve-fibres and muscle-cells : phagocytes, 

 then, play as important a part in the metamorphosis of Batrachians 

 as of Echinoderms ; and pathologists have afforded evidence of their 

 agency in the so-called active degeneration of muscles and nerves. 



A frog fed with bacteria was soon found to have them especially 

 abundant in the phagocytes of the spleen, which, therefore, is pro- 

 bably a prophylactic organ, analogous in function to the nemato- 

 calyces of Plumularia. , The author has tested in a Triton the theory 

 he holds as to the phenomena of inflammation in invertebrates being 

 primitively nothing more than a collection of phagocytes assembled 

 to devour the exciting object ; he touched a point of the tail of 

 a Triton with a small piece of nitrate of silver, and then washed it 

 with salt solution. Branched connective-tissue-cells collect round the 

 inflamed spot, and eat up blood-corpuscles, carmine granules, and 

 particles of pigment. In the frog there is evidently an active wander- 

 ing of the white blood-corpuscles. When a fully gorged phagocyte 

 dies, it is immediately devoured by another. Inflammation then is 

 not, as is ordinarily supposed, due primarily to a morbid condition of 

 the walls of the blood-vessels ; it is a struggle between phagocyte and 

 septic material, and it is in vertebrates alone that the vascular system, 

 owing to the insufficient number of extra-vascular phagocytes, takes 

 part in the struggle. The active passage of the white and the 

 passive exit of the red blood-corpuscles is rendered possible by the 

 changes in the cells of the walls of the capillaries due to the irrita- 

 tion set up by the poison. 



* Quart. Journ. Micr. Sci,, xxiv. (1884) pp. 112-7. 



