344 



Lee 



after injection, from complete paralysis of the central nervous system. 

 After systemic death it was found that the motor nerve endings were 

 almost paralysed, but that the heart was still beating. 



After a series of similar experiments upon frogs whose weights 

 approximated closely to those given in the previous experiment, it was 

 decided that the following were the minimal lethal doses of the drugs 

 for a 20-gram frog : — 



Pyridine . . -5 grain =039 gram. 



Collidine . . I grain =016 gram. 



Nicotine . ^^^ grain = 006 gram. 



Therefore, if the toxicity of pyridine be represented by TO, that of 

 collidine will be 2"4, and that of nicotine 60. From this it will be seen 

 that the toxicity of these three drugs varies in the same way as their effect 



Fig. 5, a. 



Time. 



70 70 70 68 66 



68 70 68 68 68 66 68 



68 Pulse. 



on isolated tissues. That is to say, their effects on the heart, plain muscle, 

 and central nervous sy.stem all run a parallel course, nicotine in each case 

 being much the most active and pyridine mucli the least. 



V. The Effect of Smoking on Man. 



A series of experiments were conducted upon men whose habit varied 

 from that of the novice to that of the seasoned smoker. I have described 

 below a series of experiments on the blood -pressure of men. 



The blood-pressures were taken with Martin's modification of the 

 Riva Rocci instrument, the pressure band being fixed in each case to the 

 bared left arm. The normal blood -pressure was always taken a number of 

 times before a final figure was fixed upon. I invariably found that merely 

 fixing the instrument upon the arm was sufficient to raise blood pressure 

 several mm. Hg, and the final figure was never determined until the man 

 was accustomed to all his surroundings and his blood-pressure was quite 

 constant. The habitual smokers were required to observe abstinence from 

 tobacco smoke for some six hours before being subjected to an experiment. 



Experiment 1 shows the necessity of obtaining a correct normal reading 

 of the blood-pressure before determining the effect of any drug. 



