A STUDY IN MO 11 BID AND NORMAL I" 11 Y S I O L O G V . 55 



Experiment 42. 

 A terrier. 



2 p.m. — Section made; 3:55 r. m. kymoyrapliiuii cuuiici-ted wiili tbi' carotid, the sciatic uerve 

 exposed, and one pnoumogastric cut. 



Time. Aktekial Phessuke. lEiiiT.\TiON. EEJIAKKS. 



M. Sec. (Millimetres.) 



195-20U 



0:30 Ilcinaining iiiieumogastric cut. 



1 200-210 



2:30 190-107 liegan. .Mudcrutu current. 



3 105-200 



3:30 195-200 Ceased. 



4 195-200 



4:30 195-200 



6 194-202 



5:30 19G-201 Began. Current is very intense, full force of Du liois Heyinmid coil, willi a 



largo (quart) Siemens' and llalske's cell. 

 6:30 200-203 Ceased. 



7 200-203 



9 Aninuil lulled. 



Aulopaij. — Medulla wounded deeply ui)oii riglit side, wliieli is i)ractically destroyed IVoni within 

 about four lines below to one line above the extreme point of calamus. 



Experiment 43. 



A large dog. The section was made as proven Ijy autoii.-y just below the point of tlie calamus, 

 entirely through the right side of the medulla, and more than half through the left .side. Galvani- 

 zation of the sciatic uerve with an intense current liad no effect upon blood pressure. 



All examination of tlicse experiments will show that tlicy fully confirm those of 

 Dittmar, Owsjannikow, and Heidenhain. In Experiments 41, 42, section was 

 practised entirely above the region of the calamus, and rise of arterial pressure 

 followed upon galvanization of ti nerve, as in the normal animal. In Experiments 

 42, 43, the injury to the nerve centres was within a space of four lines below and 

 above the point of the calamus, and the vaso-motor palsy was complete. I have 

 repeated these experiments at various times with identical restdts, and the evidence 

 seems to me conclusive that the chief ijovenuiKj vaso-iixdur centre in placed in the 

 lower portion of the floor of the fourth rcntricle near the point of the calamus. 



The position of the autocratic vaso-motor centre having been determined, the 

 next step in the investigation naturally is a study of the effect of wounds of tiic 

 medulla, below and above this centre, upon the bodily temperature. The following 

 experiments were performed to determine the results of sections of the medulla 

 which cause vaso-iuotor palsy. 



Experiment 44. 



A small rabbit. 



Time. Eect. Temp. RE.MAEKS. 



11:41 A.M. 102-.5F. Sliull previou.sly bared. 



11:45 Section with a very fine tenotome ; almost instantaneous fall of temperature. 



11:47 99.5 Arterial pressure 92 millimetres; galvanic irritation of the sciatic nerve caused 



no rise of pressure until the current was so strong as to produce general 

 tetanic contractions; then the mercury rose very .slowly 3 millimetres. 



11:50 99.5 



12:15 p. M. Arterial pressure 92 millimetres ; the most violent irritation of the sciatic docs 



not affect it. 



12:20 93.5 Animal breathing regularly ; killed. 



Autopsy. — Very few clot.s ; wound a full j inch behnv the lower edge of the cerebellum, nearly 



severing right half uf the cord and wuundiiiL'- the left half. 



