DEFINITION. 17 



propylic alcohol into propionic acid, and is without effect 

 upon methylic alcohol, primary isobutylic alcohol, and 

 amylic alcohol. Some bacteria will not multiply below a 

 given temperature. Thus, the bacillus butyricus will not 

 grow at a temperature,below 24°.' The lower temperature 

 does not destroy the organism, but it lies dormant until the 

 conditions are more favorable for its growth. Pasteuk 

 divided the bacteria into two classes — the aerobic and the 

 anaerobic. As the name implies, the former grow and 

 thrive in the presence of air, while the latter find their 

 conditions of life improved by the exclusion of air. There- 

 fore, different ptomaines will be formed in decomposing 

 matter freely exposed to the air, and in that\vhich is buried 

 beneath the soil or from which the air is largely excluded. 

 Even when the same ferment is present the j)roducts of the 

 putrefaction will vary, within certain limits, according to 

 the extent to which the putrefying material is supplied with 

 air. The kind of ptomaine found in a given putrid sub- 

 stance will depend also upon the stage of the putrefaction. 

 Ptomaines are transition products in the process of putre- 

 faction. They are temporary forms through which matter 

 passes while it is being transformed, by the activity of bac- 

 terial life, from the organic to the inorganic state. Com- 

 plex organic substances, as muscle and brain, are broken 

 up into less complex molecules, and so 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 combination there is more or less change in nature. In 

 one combination the atom of carbon may exist as a con- 

 stituent 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 researclies of Pasteub and others have 

 demonstrated the fact that countless myriads of minute 



• All temperatures given in this work are Centigrade, unless otherwise 

 specified. 



