The Peripheral Paralysis of the Vasomotor System Induced by Benzol *

Everyone interested in industrial medicine realizes that, with the exception only of lead, benzol is at the present time the most serious of all the toxic substances used in industry. On this account it has seemed desirable to acquire a more intimate knowledge of the details of its action upon the body and particularly its immediate, acute effects. The present discussion will bear, therefore, not upon the destruction of the hematopoietic system and the anemia that result from chronic benzol poisoning, but upon some reactions heretofore unknown,t showing the effects of benzol upon the nervous control of the circulation. Hering has shown that occlusion of the two common carotids induces a great increase in the pulse-rate and a marked rise of arterial pressure. On the other hand, when the carotids are reopened and the blood supply through them is thus renewed the heart is markedly slowed and arterial pressure is depressed again to the normal level. In addition, Hering claims that these alterations of the rate of the heart and of the tonus of the vasomotor system are the effects of a reflex which originates in a spot situated at the level of the bifurcation of the carotid artery. At this point there are nerve-endings which are sensitive to changes in arterial pressure, and from this point afferent nerve-fibers pass to the respiratory and vasomotor centers by way of what is called the sinus nerve, or, as we prefer to say, the nerve of Hering. In the investigations to be described use has been made of this new knowledge of the sinus caroticus for the analysis of the problem of the acute action of benzol. Tchernikoff and his collaborators have already shown that benzol vapor causes not only a great fall of arterial pressure, which had indeed been observed previously by