amines, others are much more rare and complex; "some are strongly alkaline and basic, others but feebly so; some are liquid, oily and volatile, others fixed and crystalline; some are very prone to change, others quite stable."
Two thirds of the known ptomaines contain only carbon, hydrogen and nitrogen. These represent the simple ammonia substitution compounds. All those that contain oxygen in addition (the so-called oxygenated bases) possess the trimethylamin molecule as their basic constituent.
Gautier has probably given the best classification of the ptomaines. He divides them into the following groups:
Monamines of the fatty acid series.
Diamines of the fatty acid series.
Aromatic ptomaines free from oxygen.
Aromatic oxygenated bases.
Unfortunately the isolation of a ptomaine from any decomposed or putrid material is a very difficult matter. This is true largely because of the great number, complexity and diversity of the other substances present in the decomposing mass and the fact that these may be at varying stages of putrefaction.
Some of the ptomaines are volatile and are decomposed at any temperature near that of boiling water. Others, very prone to undergo decomposition, may be destroyed by the action of the reagents used. Hence efforts to determine their presence and character are very apt to be attended with failure. In all of these cases, however, where a sufficient amount of a suspected food can be obtained an attempt should be made to determine the presence of any decomposition products that may have been responsible for toxic symptoms. In every case the chemical analysis must be supplemented by a bacteriological examination (much more promising of results) under both aerobic and anaerobic methods to determine the character of the microorganisms present. From pure cultures thus obtained inoculations should be made in suitable animals to determine their infectious character and filtered cultures used to determine the presence of soluble toxins.
It is quite probable, as the more recent investigations have shown, that many cases of food poisoning ordinarily classed as of ptomaine origin are in reality due to a direct infection by bacteria in the food which possess pathogenic properties or to toxins formed by them. The tendency to designate all bacterial food poisoning as ptomaine poisoning is not therefore strictly in accord with the facts as we now know them.
The resemblance of the ptomaines to the vegetable alkaloids has been noted. These two groups of compounds resemble each other in