64 



THE AMEEICAN MONTHLY 



[April, 



they may. Therefore, from a point 

 of view of comparative pathology, 

 Cohnheim's dictum, 'without blood i 

 vessels, no inflammation,' does not 

 hold ; for in Bipinnaria^ which has 

 no trace of vascular system, we see 

 a gradual accumulation of the numer- 

 ous amoeboid cells scattered through- 

 out the mesoderm. Inflammation is 

 consequently a phenomenon much 

 older, phylogenetically speaking, than 

 blood vessel, while exudation is a com- 

 paratively late development. It was 

 one of Cohnheim's leading ideas that 

 inflammation was due primarily to a 

 diseased condition of the vascular 

 walls, and that the migration of leu- 

 cocytes and the exudation of liquor san- 

 guins was a direct consequence there- 

 of. The results of Metschnikoft^'s ob- 

 sei-\'ations on the resorption during 

 metamorphosis among Echinoderms 

 ai'e moreover in complete harmony 

 with the results of histological and 

 pathological observations on Verte- 

 brates ; they have taught us that me- 

 soderm cells are able to take up and 

 to digest albuminoid granules. This 

 conclusion is strengthened by other 

 observations. After the ingestion by 

 the mesoderm cells of Bipinnaria 

 of a human blood corpuscle, we see 

 that they are completely resorbed. 

 Within the cell they swell up and 

 become clearer ; the haemoglabin is 

 then dissolved out and finally the 

 Avhole corpuscle disappears. Milk 

 injected beneath the skin of Bipin- 

 naria and PhyJlirhoe incurs the 

 same fate. If fluids containing bac- 

 teria be injected or if they develop 

 spontaneously in the wounds of these 

 animals, they will soon be found 

 within the substance of many amoe- 

 boid mesoderm cells. Both still and 

 motile forms were thus ingested and 

 found either embedded in the proto- 

 plasm of the absorbent cell or sur- 

 rounded by a vacuole. These phe- 

 nomena of the ingestion of bacteria by 

 mesoderm cells were most easily seen 

 in Botrylhis^ colonies of which, 

 when freshly gathered, contained al- 

 most invariably large quantities of 



bacteria. Within this last, Metsch- 

 nikoft' found especially a Spirochcete 

 closely resembling the S. Ober- 

 meyeri of relapsing fever, and a 

 small bacillus like the Lepra-bacillus 

 which had a spore at each end. Both 

 these forms were pursued by the wan- 

 dering cells of the Batrylhis and 

 were found ingested and absorbed by 

 them in various stages of develop- 

 ment. The victory was not, how- 

 ever, all on one side ; here and there 

 were found mesoderm cells to all ap- 

 pearances dead, with long bacterial 

 filaments projecting from them . Koch 

 has observed Bacillus anthracis and 

 the Bacillus septiscB7nice within the 

 white blood corpuscles of mice and 

 the Bacillus tuberculosis in the in- 

 terior of giant-cells, so that through- 

 out the whole animal kingdom the 

 wandering mesoderm-cells make use 

 of their ingestive power for the de- 

 struction of bacteria and similar or- 

 ganisms. These wandering meso- 

 derm-cells have lately been termed 

 by Metschnikoft" phagocytes in con- 

 nection with an article of his enti- 

 tled ' The Mesodermic Phagocytes 

 of Certain Vertebrates ' ; for he has 

 shown that intracellular absorption 

 is also found in the vertebrate meso- 

 derm. ^ Thus, for instance, during 

 the early stages of its absorption, the 

 tail of Batrachians was found to con- 

 tain a large number of amoeboid cells, 

 within which were seen remnants of 

 nerve-fibres and muscle cells. These 

 phagocytes were seen in the living 

 uninjured tail in the case of the Bom- 

 binator larva, where, at the begin- 

 ning of the metamorphosis, they col- 

 lected round the muscles of the tail, 

 the fibres of which were gradually 

 surrounded and devoured. When the 

 atrophy of the gills was in progress 

 it was easy to ascertain the presence 

 of large fully-laden phagocytes. So 

 that phagocytes seem to phi}' a part 

 in the metamorphosis of Batrachians 

 as important as that which they have 

 shown to take in the larval changes 

 oi Bipinnaria and Auricularia. 

 In order to ascertain whether, in 



