1911.] Ventilation of the Lung during Chloroform Narcosis. 349 



hirudin solution in 1-per-cent. sodium sulphate through the femoral vein, 

 and a cannula was tied into the carotid artery at the beginning of the 

 experiment while it was under nitrous oxide. The animal was placed in 

 the box, and its lung- ventilation determined for a few minutes. The glass 

 box was rapidly lifted off the slate and a sample of blood taken. The box 

 was then replaced and the respiration again recorded. 



In order to ascertain the precise effect of the inhalation of chloroform and 

 ether on the pulmonary ventilation, it would have been desirable to deter- 

 mine the normal respiratory ventilation during rest. This obviously could 

 not be determined by means of our apparatus, as an operation on the unanaes- 

 thetised animal would have been necessary ; further, it was impossible to use 

 the apparatus in the way described for human beings in Haldane and 

 Priestley's paper, for such an animal as a cat. We thought that comparisons 

 of the ventilation under chloroform with that during recovery from a low 

 percentage of some anaesthetic such as nitrous oxide, the effect of which 

 rapidly passes off and which is rapidly eliminated, would give data sufficiently 

 reliable for our purpose. Another factor which we are unable to take into 

 account is the question of the dead-space. This will no doubt vary in different 

 animals, and, cceteris paribus, the larger the dead-space in any particular 

 animal, the more air must it breathe in order to maintain a given alveolar 

 ventilation. We can find no data as to the dead-space in cats, and the only 

 satisfactory way of determining the volume of the dead-space would have 

 been by preparing a number of plaster casts of the trachea and bronchi, such 

 as Loewy* made when estimating the dead-space of the respiratory passages 

 in man. We attempted to get over this difficulty by using as far as possible 

 animals of similar size. In this paper we give the results of the effect of 

 inhalation of chloroform and ether on the apparent total ventilation of the 

 lung, regarded as the product of the average depth of respiration measured 

 in cubic centimetres at 37° C, moist, and the average frequency per minute. 



From a large number of records taken with varying percentages of chloro- 

 form and varying respiratory states of the animal prior to the anaesthetic, 

 we give a selected number to illustrate the more important points which 

 have been noticed during our experiments. 



Effect of Different Percentages of Chloroform on the Lung Ventilation. 

 In former papers we have shown that a definite danger point in chloroform 

 anaesthesia may occur during the first few minutes, and this danger point 

 depends essentially on two factors : firstly, the percentage of chloroform which 

 is being inhaled, and, secondly, upon the rate and depth of the respiration 

 * ' Pfliiger's Archiv,' 1894, vol. 58, p. 416. 



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