THE DIAGNOSTIC AND THERAPEUTIC USE 



OF MALLEIN. 



THE early investigators who raised the study of micro- 

 organisms to the rank of a science were, for the most 

 part, content with establishing the pathogenic or non-patho- 

 genic characters of bacteria, and morphological considerations 

 played an important part in the chain of evidence by which 

 it was proved that definite species of bacteria may stand in 

 direct causal relation to disease. At the present time, how- 

 ever, the growth of knowledge concerning bacteria chiefly 

 takes place by the application of methods which are identical 

 with those which have created physiology, and the interest 

 which surrounds the discovery of a new micro-organism 

 soon disappears, because researches conducted upon 

 physiological lines are absolutely necessary before the full 

 importance of the discovery can be appreciated. The 

 conditions which govern its spread and mode of repro- 

 duction have to be determined, but, above all, the 

 exchange of material which a microbe exhibits needs 

 investigation, and it is this problem which has attracted so 

 many workers. 



The products of bacterial life have in several cases been 

 proved to be even more harmful than the microbes them- 

 selves, while, on the other hand, filtrates of bacterial cul- 

 tures have been employed to confer immunity, a state which, 

 when established, may be transferred from one animal to 

 another of the same or even a different species. Apart 

 from changes in the culture media which are produced by 

 the exchange of material consequent on bacterial life, the 

 microbes themselves may die, and by subsequent disinte- 

 gration give rise to substances which possess neither toxic 

 nor protective properties, but are capable of causing pro- 

 found constitutional changes among which fever and local 

 inflammatory disturbances are prominent symptoms. To 

 this class of bodies belong those bacterial proteines which 

 Buchner, Romer and others have investigated, and pro- 



