In the preceding parts of the investigation of the products obtained by the destructive distillation of animal substances, I have entered fully into the method of treating the raw material, and have shown the existence in it of not less than three different series of bases; one, that of which methylamine is the type; a second, of which picoline is an example; and a third series, not yet further examined, to which the provisional name of pyrol bases has been applied. Besides these, aniline is also met with, but whether as an isolated substance or accompanied by the other members of its series, cannot be determined, as none of them possess sufficiently distinctive reactions to permit their detection in a complex mixture.