8 



SCIENCE. 



[N. S. Vol. XX. No. 496. 



connected with the observation is this, that 

 two bodies at least are concerned with the 

 sugar in the reaction. One of these may 

 act as a catalyzer for the other, or, taken 

 together, both may act in the manner of 

 the complement and intermediary body of 

 Ehrlich, of which more will be said below. 

 The point of importance here is that the 

 theory of this oxidation has shifted around 

 so as to become a strictly chemical one. As 

 long as some specific action of the cell was 

 called in to account for the observed phe- 

 nomena the biologist rather than the chem- 

 ist was interested in the solution of the 

 problem. It now appears that "the chem- 

 ical factors are the main ones to be con- 

 sidered in the final effect. It remains, of 

 course, true that the oxidizing ferments 

 must be always the products of cell action, 

 but the important idea suggests itself that 

 they need not necessarily be produced by 

 the same body which is later to use them. 

 If investigators succeed in showing more 

 specifically the nature of the two sub- 

 stances, it may be found possible to secure 

 them from other animals and introduce 

 them when needed, much as antitoxins are 

 introduced. 



Many of those present doubtless recall 

 the beginnings of what is known as the 

 germ theory of diseases. From his success 

 in developing a satisfactory theory of alco- 

 holic fermentation, which became of vast 

 importance in the brewing and wine in- 

 dustries, Pasteur was led to study the 

 causes of failure often noticed in practical 

 fermentation. Beers and wines sometimes 

 become diseased and spoil in the process of 

 making. They turn sour, or for other 

 ■reason become unfit for use. The explana- 

 tion of this was found to lie in the presence 

 of foreign ferments which induce new reac- 

 tions. As a preventive of such diseases 

 sterilization and pasteurization processes 

 were suggested and have become common 

 in many industries besides those for which 



first developed. From sick beers and wines 

 Pasteur was led to study sick silkworms, 

 then a question of great commercial in- 

 terest in France, and found the cause of 

 the malady and later a method of preven- 

 tion. Following this wonderful work, men 

 began to look for microorganisms else- 

 where, and in the course of a few years 

 specific bacteria were described as the ac- 

 tive agents in inducing cholera, anthrax, 

 tuberculosis and other dread diseases. Ac- 

 cording to the germ theory, the invasion of 

 certain tissues of man or the higher ani- 

 mals by these bacteria is the real cause of 

 the disease in question. It must be re- 

 called that these organisms are extremely 

 minute. Many millions of them would be 

 required to produce the volume of a pin 

 head, and that anything so small could give 

 rise to cholera or typhoid fever seemed at 

 first utterly unreasonable. That these 

 minute things are the actual agents of 

 many diseases there can now be no doubt. 

 It remains to discover how they act. At 

 first their effects were assumed to be largely 

 mechanical and in the direction of the de- 

 struction of tissues, but in many eases the 

 tissue destruction is of secondary impor- 

 tance. The notion gradually developed 

 that many of the ' disease-producing bac- 

 teria are active through the poisonous prin- 

 ciples or. toxins which they elaborate. The 

 toxins are complex chemical substances re- 

 sembling in properties some of the alka- 

 loids, or possibly belonging to the group 

 of enzymes. At any rate, as soluble chem- 

 ical agents, they are able to diffuse through- 

 out the body and interfere with its normal 

 functions. We appear to have then a 

 chemical theory back of the germ theory 

 and this development is proving of the 

 highest importance from both theoretical 

 and practical standpoints. The theory of 

 the production of toxic substances by the 

 bacteria involved, of course, no new as- 

 sumption. Chemists had been long fa- 



