Abstract

Our main conclusions may be stated as follows:

1. Histamine, β-iminazolyl-ethylamine, a substance which stimulates plain muscle tissue in minute doses, which depresses the circulation, and which causes a shock-like prostration when administered in doses that lie beyond the limits of toleration, is a widely distributed constituent of all animal tissues, organ extracts, and enzymatic products, such as Witte's peptone and erepton, whether derived from animal or vegetable proteids. While certain bacteria, as is well known, are capable of producing the base by decarboxylating histamine, its occurrence as here described is entirely independent of microorganisms. Hydrolysis of pure proteins, such as crystallized albumin, pure casein, and edestin, with hydrochloric acid yields a base which is identical in our opinion with histamine or which at best is a similarly acting substitution product of it.

2. It follows from the above that histamine is a constituent of our diet and that we daily consume no inconsiderable amount of the base, some of which is present in the form of the free base or a simple salt, while more of it is in all probability produced in the course of digestion. We base the latter assertion on the fact that enzymatic products, such as Witte's peptone and erepton, contain the base in larger amount than the original material from which these products are derived.

3. We have suggested that histamine plays an important role as stimulant for the gastric and intestinal musculature and also as a dilator of capillaries during digestion. This last action is probably also of importance for organs in general, during periods of increased activity. It has also been suggested that histamine is the most powerfully acting among the depressant substances which have their origin in mutilated tissues, and hence plays the leading rôle among the chemical factors concerned in traumatic shock.

4. Histamine is the plain muscle-stimulating and depressor constituent of the posterior lobe of the pituitary gland. The physiological and chemical evidence in favor of the identity of the two principles coincide at every point. As histamine occurs to some extent in all tissues, it can no longer be considered to be a hormone or substance specific to the pituitary gland. We have no explanation to offer at present for the relatively high concentration in which the base is found in the posterior lobe of this organ.

5. We have given a few data to prove that the animal organism can tolerate considerable amounts of histamine when it is given by mouth and have gathered from the writings of other investigators the facts now known and the surmises in regard to the excretion of the base and its fate in the organism.