A STUDY IN xMOKBIP AND NORMAL PHYSIOLOGY 



149 



Time. Aiitekial Pressure.* KEHAKKS. 



H. M. tiec. 



210-230 



220-230 

 3:22 220-230 



21.i-225 



210-220 



210-225 

 3:23 210-220 



Autopsy. — Right side of brain: tlie whole region near the sulcus crnoiatus washed away; the 

 veuti-icles uncovered. Left side of brain: the same region gone excepting in its extreme outer 

 portion. 



In studying these experiments, it will be observed that they were performed 

 upon dqgs with the vagi uncut. In the first of the two, the Hitzig's region 

 was destroyed mechanically witliout the arterial pressure being affected at all, it 

 remaining steady from 215-280, rising and falling within narrow limits. One 

 minute and forty seconds later, a strong stream of water was forced into one tre- 

 phine opening and through to the other carrying out with it masses of brain. The 

 effect of this procedure was remarkably little. There was no fall of the arterial 

 pressure whatever for five minutes, and then the diminution was so slight and tem- 

 porary that probably it had its source in some other cause than the operation. 

 Some minutes later, artificial -respiration being suspended, an enormous rise of the 

 arterial pressure occurred, showing that the general vaso-motor svsteni was intact. 



In the second experiment, a mild electrical current sent through both Hitzig's 

 regions produced no rise of pressure whatever. Later, a very powerful current 

 produced a decided rise of pressure, to account for which, the violent tetanus of 

 the anterior part of the bbdy seemed itself sufficient. At 3:18:40 v. M., the surface 

 of the Hitzig's cerebral region was mechanically destroyed. The muscular move- 

 ments induced caused some momentary derangement of the circulation. In twenty 

 seconds, however, the arterial pressure had returned to the place whence it started 

 at 3:12 p. M., *'. e., from 225-240. It did not vary decisively from this until 3:21 r. .M., 

 when a stream of water was forced violently into the brain, producing great destruc- 

 tion. After this there was a very slight fall of pressure, the mercury descending 

 to 210-230; a fall remarkably small considering the extent of the injury and 

 the probability of the occurrence of severe shock. 



It will be seen that these experiments are in accord, and warrant the following 

 conclusion: that when the vagi are uncut, neither the application of galvanic cur- 

 ^ rents to nor the mechanical destruction of Hitzig's region has any decided inlitience 

 upon the blood pressure. 



There was a distinct sh)wing of tlie pulse produced by the application of the 

 galvanic current; which, of course, indicates an excitation of the pneumogastrics. 

 Now, it is well known, that galvanization of a sensitive nerve in the dog with the 

 vagi uncut often fails to induce rise of the arterial pressure — although it induces 

 vaso-motor spasm — because it inhibits the cardiac action by stimulating the 

 pneumogastric centres. As such an influence was manifest in the case under 

 consideration, the following experiments were performed upon dogs with cut vagi: — 



