34 



Dr. C. Bolton. Physiological Action of a [Mar. 20, 



injection of 1/10 gramme of the poison was administered. After the second 

 injection the pressure rose to 169 to 170 mm. Hg in 33 seconds and then 

 fell rapidly to 30 mm. Hg above zero owing to heart failure. 



This pressure curve cannot be divided into two parts as described above 

 when the vagi are intact. The pressure gradually rose in a long single curve 

 to its highest point, and from this point it gradually fell. 



Respiration. — The respirations were nest affected till the blood pressure 

 finally fell, except that they became slightly shallower. Large inspiratory 

 gasps were taken for three minutes after the blood pressure had fallen to 

 its lowest limit. 



Experiment 5. — Cat, weight 3220 grammes. Both vagi divided before 

 injection. Poison 1/10 gramme (= 0"034 gramme per kilogramme). 



Blood Pressure. — The blood pressure began to rise six seconds after the 

 injection of the poison, and attained its maximum height of 216 mm. Hg 

 in 86 seconds, having risen from 174 mm. Hg. After this there was a steady 

 fall till the heart stopped in 146 seconds. 



Heart Beats. — Immediately before injection the rate of the heart was 

 258 per minute, and when the blood pressure had risen to its maximum 

 point the rate was unaltered. Before the final fall it had increased to 

 261 per minute. There was no fall in the blood pressure during the early 

 stage of poisoning, and the pulse rate did not notably increase towards the 

 end of life. 



Respirations. — The respirations were not affected until the blood pressure 

 fell, when they became irregular as the heart stopped, inspiratory gasps 

 continuing at intervals for about three minutes after the blood pressure had 

 reached its lowest point. 



Excitation of Vagus. — The left vagus was stimulated, the strength of 

 current being 10 (secondary coil at 10 cm. distance). The stimulation was 

 continued for 10 seconds. Before stimulation the blood pressure was 

 216 mm. Hg, and at the end of stimulation it' was 210 mm. Hg ; for the 

 next six seconds it gradually fell to 190 mm. Hg, and then rose almost to 

 its former height (210 mm. Hg). The rate of the heart fell by about eight 

 beats per minute. 



The vagus was again stimulated 50 seconds later, the strength of the 

 current being increased to six and the time to 12 seconds. This time there 

 was no obvious effect produced upon the blood pressure. Before the poison 

 was administered a stimulus of strength 12 applied to the left vagus produced 

 an immediate fall in the blood pressure of over 30 mm. Hg. 



Experiment 6. — Cat, weight 2720 grammes. Bight vagus divided before 

 injection. Poison 1/15 gramme (= - 024 gramme per kilogramme). 



