ON ANESTHETICS. 275 



is regarded as more dangerous than ether. I have attempted in this 

 report to indicate the precise reason of the difference. And in conclu- 

 sion, in order to illustrate the point that it is useless to compare drugs 

 without reference to their quantities, I give two records. One, of the 

 first twenty-five minutes of a chloroform anaesthesia in which the per- 

 centage was raised for a few minutes up to 3 per cent., then dropped to 

 2, 1'5, 1, and 0'5 per cent, (and subsequently kept up for six hours at 

 below 1 per cent.); the second, of an ether anaesthesia at 24 per cent., 

 in which respiration ceased at the end of twenty-five minutes. 



APPENDIX II. 



On the Rate of Assumption of Chloroform by the Blood; and the Per- 

 centages of Chloroform found in the Blood of Cats at the Asphyxial 

 Point, using different Strengths of Chloroform-Air Mixture. By 

 Dr. G. A. Buckmaster and Mr. J. A. Gardner. 



In our last report we brought forward evidence to show that the 

 chloroform content of the blood rises in the initial stages of anaesthesia 

 with great rapidity to a value which approaches a maximum. During 

 this period the quantity of chloroform in the blood appears to affect 

 particularly the respiratory centres, so that breathing becomes slower 

 and often ceases during the first few minutes of anaesthesia, and it may 

 be necessary to resort to artificial respiration in order to prevent the 

 animal dying. The cessation or slowing of respiration at this stage is 

 most liable to occur with high percentages of chloroform — i.e., above 

 2 per cent. Thus a definite danger-point occurs in the first few 

 minutes of anaesthesia, owing to paralysis of the respiratory nervous 

 mechanism. The steepness of the curve representing the initial rise 

 of chloroform in the blood is also increased by increasing the strength 

 of the chloroform-air mixture inhaled. If the animal naturally passes 

 this stage, and is restored either by stopping the chloroform inhalation-or 

 by artificial respiration, then, on continuing the anaesthetic, the amount of 

 chloroform in the blood quickly rises again towards a maximum value. 

 An equilibrium between the pressures which determine the amount 

 of chloroform in the blood subsequently appears to be obtained, the 

 processes of intake and output at the surface of the lung going on side by 

 side. This state of equilibrium is reached and may persist for a con- 

 siderable length of time. During this period the animal can always 

 be killed by chloroform, even though the percentage of chloroform in 

 the blood rises only very slowly. We would emphasise the point that 

 while the absolute difference between the amounts of chloroform in the 

 blood throughout this anaesthetic stage and that present at death is very 

 small — e.g., 20 mg. per 100 compared with 45 mg. per 100 — the 

 relative difference is considerable — i.e., more than double. 



