564 Messrs. G. A. Buckraaster and J. A. Gardner. [Mar. 7, 



Conclusions. 



From the tables and curves that have been given, we consider that the views 

 expressed in the earlier part of the paper, which were based on a much larger 

 number of experiments undertaken with various other objects, and 

 with which this paper does not deal, are justified. 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 is necessary to resort to artificial respiration in 

 order to prevent the animal dying. With the percentages of chloroform that 

 have been employed, we have never noticed failure of the heart at this stage. 

 The cessation or slowing of respiration at this stage is, as might have been 

 expected, more liable to occur with high than with low percentages of 

 chloroform. Sudden failure of the heart's action has never been noticed by 

 us in cats under the conditions of our experiments, where no percentages of 

 chloroform above 5 have been employed. We have found that a definite 

 danger-point occurs in the first few minutes of anaesthesia, owing to paralysis 

 of the respiratory nervous mechanism. 



If the animal naturally passes this stage, which is marked on the curves 

 between X and Y, as in Experiment III, or 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 factors 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 stage extends from point Z onwards. 



This state of equilibrium is reached, and may persist for a considerable 

 length of time. The exact length of this period differs with different 

 individuals, and even in the same individual in different experiments. 

 During this period the animal may die at any moment should any disturbing 

 influences come into play, and therefore the state is not one of safety. 

 During this period the animal can always be killed with chloroform, even 

 though the percentage of chloroform in the blood rises only very slowly. 

 We would emphasise the point that the difference between the amount 

 of chloroform in the blood throughout this anaesthetic stage and death is 

 very minute. It will be noticed that the difference between the percentages 

 of chloroform in the blood at the point where the corneal reflexes vanish 

 and the maximum values attained are by no means large in actual value, 



