74 POPULAR SCIENCE MONTHLY. 



ically and physically the same as some of their best nutrients — save in 

 having opposite powers of rotation. 



Taking into consideration that micro-organisms can withstand tem- 

 peratures and chemicals fatal to man, the slow development of infectious 

 diseases is most probably intimately connected with an insufficiency 

 of assimilable food. This food it may be assumed can only be obtained 

 by symbiosis either with other micro-organisms or products of cell 

 activity in the system itself. 



It is claimed that the Anopheles mosquito is the intermediate host 

 of the human malaria and the Culex that of the bird, but not vice versa. 

 These mosquitoes undoubtedly do not select the spores of their respective 

 parasites and avoid the others, but there must exist conditions in the 

 system of the respective mosquito which allow of the propagation of one 

 kind and not the other — and these conditions, I take it, are food 

 assimilable ones. 



White mice are immune to splenic fever, other mice very suscep- 

 tible. Since the blood of white mice is more alkaline than that of the 

 others — and such blood when made less alkaline becomes a good medium 

 for the cultivation of the anthrax bacillus — it has been claimed that 

 the alkalinity produces the immunity. On the other hand it has been 

 found that alkalies are not particularly harmful to the anthrax bacillus 

 — therefore, it seems to me, that alkalinity, as such, is less of a factor 

 than its consequent effects upon the nutrients of the bacillus. 



Pasteur demonstrated that micro-organisms select one of two optical 

 isomers, and Fischer proved that it is not only a question of optical 

 antipodes in different sugars, but amongst a great number of geomet- 

 rical forms few fulfil the requirements of the cells — furthermore he is 

 of the opinion that many chemical processes in the system are affected 

 by molecular geometry. 



The albuminoids are the most important constituents of the living 

 cells and since they are synthetically formed from the carbohydrates of 

 the plants, Fischer believes that the geometrical structures of their 

 molecules, as far as asymmetry is concerned, are essentially like those 

 of the natural hexoses. Thus it seems that configuration plays a most 

 important role in making food assimilable — be it in converting inactive 

 into active modifications or vice versa or the production of one optical 

 isomer instead of the other, or some other change of configuration, the 

 consequence would be a different behavior toward the ferments, 

 enzymes and sporozoa. 



We now come to another feature which also may be of physiological 

 interest, namely: the fact that the alkaloids largely used for thera- 

 peutical purposes, such as quinine, cinchonine, quinicine, conchinine, 

 strychnine, brucine and morphia can, like micro-organisms, bi-part 

 racemic forms. Thus cinchonine separates as salt from the inactive 



