pig which succumbs acutely to an intravenous injection of horse serum, and which are diagnostic, when properly considered, of true anaphylaxis in this animal. These lungs owe their state to a tetanic contraction of the bronchial muscles, so that the enclosed air is imprisoned in the alveolar sacs and can not escape even when the lungs are completely excised (see Fig. 1). Now, any adequate stimulus which causes an enduring contraction of these muscles while respiration goes on will produce a greater or less approximation to the lung picture of anaphylaxis. Such adequate stimuli are furnished by a large number of substances, of which we may mention muscarine, eserine, pilocarpine, digitaline, veratrine, morphine barium chloride and the salts of many heavy metals (Dixon and Brodie). Nobody, however, would state that the substances cause anaphylaxis, that they are anaphylatoxins, even though they do produce apparently a lesion of anaphylaxis, for it is perfectly obvious to every one that it is inadmissible to conclude from the identity of reaction produced (in the example chosen, the anaphylactic lung) an identity of the causative agents, as this leads to the ridiculous conclusion that eserine, muscarine, etc., are identical. The same reasoning is applicable to the degradation products obtained by chemical or biological means from proteids. It is not surprising that decomposition products of the infinitely complex proteid molecule should yield substances which are toxic to an organism, and which produce anatomical and functional changes similar to those observed in anaphylaxis, but this does not permit the conclusion that the same decomposition products are formed and exert their actions in true anaphylaxis; such reasoning commits the same error which was mentioned before. It must be insisted that an identity in the biological response caused by a variety of substances permits only the conclusion that these substances are functionally identical, not that they are chemically or so to say, morphologically identical. This confusion is widespread, and at present dominant; it is especially due to the per se valuable and interesting contributions of Friedberger and his colaborers. Friedberger is convinced that the poisonous mixture which he produces by biological methods in vitro is identical with the causative agent or agents in true anaphylaxis, and in most of his recent work the symptom complexes studied were not true anaphylaxis, but the symptoms produced on first injection by his anaphylatoxin.
The question has probably occurred to the reader why this problem was not approached directly, why, for example, the serum of animals in anaphylaxis was not examined for the presence of these degradation products which are said to play such an important rôle. The test can easily be made, for the split products of proteids which have an albumose or pepton character give the biuret reaction. But no investigator, as far as I am aware, has been able to obtain more than a very feeble or