THE 



BRITISH NATURALIST. 



NEW SERIES, 



PHAGOCYTES. 



BY A. H. YOUNG, M.B., F.R.CS. 



PROFESSOR OF ANATOMY IN OWENS COLLEGE, MANCHESTER. 



That the struggle for existence between the simple and primitive 

 forms of life is as keen as that between more highly developed and 

 complex organisms is well known to all naturalists; but whilst one 

 may look with comparative indifference on a warfare between the 

 higher forms of life which at the most ends in the destruction of 

 the individuals actively engaged, and which is, in a sense, carried on 

 outside and independent of ourselves, the case is very different when 

 the battle of the lower and simpler forms of life is being fought out, 

 since not unfrequently we have to provide in our own persons both 

 the battle ground and some of the combatants — and the result of 

 the conflict may be fatal to us. 



It is beyond question that many diseases are due to the intro- 

 duction from without of viable micro-organisms — germs — but it is 

 not easy to explain satisfactorily, how it is that the access of germs 

 capable of producing definite disease does not always do so. It 

 is a matter of common knowledge when a number of individuals 

 are exposed to infective diseases, that some fall victims whilst 

 others escape entirely. To put this more definitely, it can be 



EXPLANATION OF PLATE X. 

 Fig. i. — Amoeba with nucleus and food particle. 



Fig. 2. — Amoeba living amongst bacilli, some of which it has taken up. 



Fig. 3. — Hind part of a Daphnia infected with Monospora. a, Spores surrounded with Phagocytes. 

 Fig. 4. — Spores of Monospora, showing changes produced by Phagocytes. 



(Figs. 2, 3, and 4 are slightly altered from Metchnikoff.) 



