FISSION FUNGI AS CAUSAL AGENTS OF DISEASE. 643 



organ has occurred. Besides, it may be easily seen that Preference 

 the nutrient material present in the body of warm- nutrient con- 

 blooded animals, and the temperature of the body, are j^ 8 in the 

 not specially favourable for the pathogenic organisms, 

 and do not enable them to multiply more rapidly than 

 the saprophytes ; for in a dead body, kept at 37 C., the 

 saprophytes obtain the mastery in a short time, even 

 when they have been introduced in smaller numbers 

 than the pathogenic bacteria. 



This want of influence of the movements of the Resistance t 3 

 fluid, of the tension of the oxygen, of the secretory ce iis? ving 

 functions, of the temperature, and of the chemical com- 

 position of the body on the one hand, and on the other 

 hand the fundamental alteration of the conditions of 

 existence of bacteria when death of the body occurs, 

 shows us that it is in the protoplasm of the living cells 

 that the most important factor, and that which regulates 

 the differences in the behaviour of saprophytes and 

 parasites, lies. Only those bacteria can be reckoned in 

 the latter class which are able to obtain the mastery, 

 and to multiply in concurrence with the living cells, 

 while the saprophytes are not able to grow when sub- 

 jected to the influence of the living cells, but on the 

 contrary die. Thus the living cells would form the seat 

 where the body carries on the battle with the invading 

 bacteria, where the saprophytes are destroyed, and where 

 the parasitic bacteria gain the victory. 



This view of a battle between the cells and bacteria, 

 for a time only obtained by deduction, seems to have 

 gained a definite support from the experiments of 

 Metschnikoff. He was able in experiments with a Metschnikoffs 

 yeast parasite of daphnis, as well as in experiments with 

 anthrax bacilli, which he introduced under the skin 

 of frogs, to observe that bacteria are taken up by 

 leucocytes ; the bacteria were gradually destroyed in the 

 substance of the leucocytes, being as it were, digested. 

 Metschnikoff at a later period made similar observa- 

 tions in rabbits and guinea-pigs which he had in- 

 oculated with attenuated anthrax bacilli. Nevertheless, 

 Metschnikoff's experiments are by no means free from 



