108 M. AKMAND RUFPER. 



In 1887, Metschnikoff found that the leucocytes present in the 

 mucus covering the tonsils of healthy people frequently contained 

 micro-organisms. In 1885^ Ribbert and Bizozzero examining 

 the Peyer's patches and vermiform appendix of healthy rabbits, 

 showed that the walls of these organs are crammed with an 

 enormous number of degenerated micro-organisms ; both these 

 observers attributing the death of the parasites to the action of 

 the cells of the part. In 1890, the writer^ demonstrated the 

 fact that the leucocytes which wander out between the epithe- 

 lium cells to the surface of the lymphoid organs of various 

 animals — more especially rabbits — are frequently filled with 

 micro-organisms. The leucocytes (microphages) carry their prey 

 into the interior of the tissues, but, being weakened by the 

 secretions of the microbes they contain, are frequently eaten 

 up by larger cells (macrophages), which resemble in all particu- 

 lars the macrophages described by Metschnikoff in pathological 

 specimens. The writer has shown that the same process takes 

 place in the tonsils also. The conclusion to be drawn from 

 these researches is, that the mesodermic cells, of healthy animals 

 even, have the power of absorbing, destroying and digesting 

 micro-organisms. 



A little consideration shows that the lungs and intestinal 

 tract, which are the organs most likely to be attacked by micro- 

 organisms, are provided with a large number of mesodermic 

 cells. Attention has been drawn to the fact that mesodermic 

 cells proceed to the surface along the whole length of the ali- 

 mentary canal and destroy micro-organisms. Moreover, 

 immediately below the layer of epithelium cells and along the 

 whole length of the intestinal tract, a layer of adenoid tissue is 

 spread out like a lymphatic gland. Every micro-organism, 

 therefore, which, by any chance, passes the first barrier of epi- 

 thelium cells must run the gauntlet of this adenoid layer and 

 most probably be destroyed. 



In the lungs, similar macrophages line the alveoli and remove 

 dust, particles of charcoal, &c., which, by gradual accumula- 

 tion, might choke the air-passages. Surgeons know — and Sir 

 I Armand lluffer, loc. cit. 



