394 PROFESSOR C. R. MARSHALL ON THE 



of large doses no instance of stoppage in the extreme diastole, which is characteristic 

 of tetra-methyl-ammonium chloride and other substances stimulating the vagal nerve 

 endings, occurred. When a hypertonic solution (2*15 per cent.) was dropped on to 

 the exposed heart a slight increase in the frequency of the beats occurred, but no 

 diastolic relaxation or cessation of the heart followed, notwithstanding repeated 

 application. 



In rabbits the intravenous injection of 1 or 2 mg. per kg. body- weight is usually 

 followed by a slight fall of blood-pressure. The fall commences a few seconds after 



Fig. 5. — Effect of tetra-ethyl-ammonium chloride on the respiration and blood- pressure of a decerebrate 

 rabbit. Weight 2225 g. Letters as in rig. 3. The respiration was recorded by connecting one 

 limb of the tracheal cannula to a tambour. 



the completion of the injection, and with a dose of 2 mg. per kg. extends to about a 

 quarter the height of the normal blood-pressure. Recovery occurs in two to three 

 minutes. Doses of 10 mg. per kg. body-weight cause a more rapid and somewhat 

 more profound fall of blood-pressure, but the extent is rarely more than half the 

 normal height. With doses of 25 mg. per kg. body-weight a fall to about one-third 

 the normal height occurs (fig. 6). The fall is maintained for one to two minutes, and 

 then gradual recovery follows. As no slowing or apparent weakening of the heart 

 occurs, the fall would seem to be due to a vascular effect. In decerebrate animals a 

 slight rise may precede the fall of blood-pressure (fig. 5). 



The blood-pressure of cats is much less susceptible to the action of tetra-ethyl- 

 ammonium chloride than that of rabbits. In these animals an intravenous injection 

 of 10 mg. per kg. body-weight usually produces no change, and even doses of 25 mg. 



