BACTERIAL PROTEIDS. 31 



and thrive in the presence of air, while the latter find their condi- 

 tions of life improved by the exclusion of air ; therefore, different 

 products will be formed in decomposing matter freely exposed to the 

 air, and in that which is buried beneath the soil or from which the 

 air is otherwise largely excluded. Ignorance of this fact has led to 

 some serious mistakes in toxicological work, as we shall see further on. 



It is more than probable that most, if not all, ptomams result 

 from the cleavage action of bacteria on the constituents of the me- 

 dium in which they grow, and it follows from this that the kind of 

 ptomain found in a given case will depend upon the stage of the bac- 

 terial disintegration of the constituents of the medium. Regarded 

 as the results of cleava,ge action, ptomains are transition products in 

 the processes of bacterial decomposition. They are temporary forms 

 through which matter passes while it is being changed, by the ac- 

 tivity of bacterial life, from the organic to the inorganic state. 

 Complex organic substances, as muscle and brain, are broken up into 

 less complex molecules, and thus the process of chemical division 

 goes on until the simple and well-known final products, carbonic acid 

 gas, ammonia and water, result; but the variety of combinations 

 into which an individual atom of carbon may enter during this long 

 series of changes is almost unlimited, and with each change in com- 

 bination there is more or less alteration in nature. In one compound 

 the atom of carbon may exist as a constituent of a highly poisonous 

 substance, while the next combination into which it enters may be 

 wholly inert. 



It was formerly supposed that putrefaction was simply oxidation, 

 but the researches of Pasteur and others have demonstrated the fact 

 that countless myriads of microorganisms are engaged constantly in 

 transforming matter from the organic to the inorganic form. If a bit 

 of flesh be locked up so that these little workers cannot reach it, it will 

 remain unchanged indefinitely. It may be asked if any of the 

 changes occurring during putrefaction are to be regarded as purely 

 chemical. Without doubt, many of the secondary products of putre- 

 faction arise from reactions between antecedent and more complex 

 substances, or by the action of oxygen, water, and reducing agents 

 upon primary products. Ptomains formed in this way may be re- 

 garded as the indirect results of bacterial life. 



While some of the basic substances formed by bacterial growth 

 are intensely poisonous, it is not probable that any ptomain can be 

 regarded as the most potent product of one of the pathogenic bac- 

 teria. It follows, therefore, that we must seek for the specific poisons 

 of the infectious diseases among other chemical compounds produced 

 by bacterial growth. 



Bacterial Proteids. — Our knowledge concerning these substances 

 still remains quite imperfect and many difficulties arise in discussing 



