CHLOROFORM A POISON 



21 



The calculation was made as follows : The total amount 

 of vapour in the residual and supplemental air was calculated, 

 and to this amount was added the amount of vapour in the 

 inspired air. Having then estimated the total volume of 

 inspired, residual, and supplemental air, the percentage of 

 vapour in them was calculated from the above data. The 

 following equation expresses the method : 



( ' , \ x 100 = percentage of chloroform in alveolar air after one respiration. 



Where x = amount of anaesthetic in the inspired air in c.c. 



Where y = amount of anaesthetic in supplemental + residual air in c.c. 



Where a = inspired air in c.c. 



Where b = supplemental + residual air in c.c. 



It will be noted that in the above table in the case of the 

 100 c.c. respirations, although actually less vapour is being 

 inspired than in the 250 c.c. respirations, nevertheless the 

 concentration rises more rapidly in the first than in the second 

 case. In the first case only 4 c.c. of chloroform are being 

 inhaled at each respiration, whilst in the second case 5 c.c. 

 are being taken in. The reason for the more rapid rise of 

 alveolar concentration in the first case is to be sought in the 

 fact that although less is being taken, still less to a greater pro- 

 portion is given out at each respiration. Taking the 250 c.c. 

 respirations, and the first of the series given, 5 c.c. is taken 

 in, and 3*45 c.c. given out, the amount retained being accordingly 

 1*55 c.c. Taking the 100 c.c. respirations, and the first of 

 the series given, 4 c.c. is taken in, and 1*43 c.c. given out, the 

 amount retained being 2*57 c.c. If it were desired to exactly 

 compensate for the diminished depth of the respirations, the 

 100 c.c. respirations would have to contain not 4 per cent, but 

 only 3 per cent, of chloroform approximately. 



