io6 NATURAL SCIENCE. Feb.. 



to the medical faculty ; and, like Pasteur's, Dr. Maclagen's explanation 

 does not account for the fact that the microbe can be grown outside 

 the body where the nidus does not exist. 



And how is the change in the organism supposed to be brought 

 about ? Pasteur believes the attenuation of the virus to be due to the 

 action of the oxygen of the air, except, of course, in those cases where 

 it is passed though a series of animals, or where the change is partly 

 attributed to heat ; but it is difficult to understand in what way 

 oxygen could alter the character of a living organism so as to cause 

 it to produce varying effects. Is there any case known of an organism 

 altered in such a way ? There are three cases among the organisms 

 we are considering, in which the essential characters of the species are 

 said to have been thus changed by the method of cultivation : — 



(i.) Buchner has stated that by successive cultivations he has 

 transformed the bacillus of anthrax into the harmless hay bacillus. 

 He likewise claims to have transformed the hay bacillus into the 

 deadly bacillus of anthrax. 



(2.) A bacillus found on the seeds of Alexus precatovius (an Indian 

 and South American leguminous plant used in certain diseases of the 

 eye), and apparently identical with the hay bacillus, is, according to 

 Sattler, capable of being transformed into a disease-producing form. 

 An infusion of the seeds, known as jequirity, is made and several 

 cultivations of the bacillus started from this in the ordinary sterilised 

 media. The change in the nature of the bacillus is supposed to be 

 effected by growth in the original jequirity fluid, and to be retained 

 in the successive cultivations, since all these were found to produce 

 severe ophthalmia ; and not only did Sattler suppose the original 

 jequirity bacillus was thus modified so as to produce disease, but 

 that germs of other harmless forms which might settle down in the 

 jequirity solution likewise became pathogenic. 



(3.) The third case is that of a common vaon\d, Aspeygilhis, which 

 has been found to produce death in rabbits when its spores are 

 introduced into their systems, although not in the proper sense of the 

 term a pathogenic form. 



Dr. Klein has carefully examined these cases, and repeated the 

 experiments, with the result that all break down as examples of the 

 change of septic into pathogenic microbes. " I feel sure," he says, 

 " anyone might as soon attempt to transform the bulb of the common 

 onion into the bulb of the poisonous colchicum." Other observers 

 have corroborated Klein's conclusions. 



Ought we, then, to believe that by a series of cultivations a 

 microbe can lose the power of producing disease which it once 

 possessed ? 



If the microbes of disease can be altered so as to produce a 

 modified disease, it ought to be possible to produce, say, a lactic acid 

 microbe, which would produce a modified lactic fermentation ; and 

 further, such a modified fermentation should protect the liquid from 



