410 



Dr. E. H. Embley. 



[June 13, 



instance, in experiments with vagi cut, occurs within 15' when the con- 

 centration of ethyl chloride exceeds 20 per cent. 



In administrations not exceeding 15' duration (these statements do not 

 hold for periods exceeding this) in addition to the above-mentioned effect 

 on the blood-pressure brought on through the vagus mechanism, the pressure 

 falls from paralysis of the cardiac muscle when the concentration exceeds 

 20 per cent. The rate of fall of blood-pressure always varies with the rate of 

 the respiration. 



(5) 5 to 7 per cent, of ethyl chloride vapour in the air respired appears to 

 be the limit of safety from syncope in dogs for prolonged and continuous 

 administration. If this concentration be exceeded, it is inadvisable to continue 

 the administration beyond abolition of the corneal reflex, otherwise syncope is 

 very probable. 



These conclusions with regard to the effects of ethyl chloride upon dogs 

 likely apply to man. In man I have observed syncope occur in two 

 instances and recovery to take place with a sudden return of pulse of fair 

 volume and sudden replacement of the colour of death by that of life. 

 From analogy with experimental results I regard such syncope as due to 

 vagus inhibition. These conclusions, however, cannot be expected to hold 

 good in clinical instances of failing heart and other morbid states that may 

 embarrass recovery. A sound heart is able to free itself from vagus arrest, 

 but the degree of depression caused by ethyl chloride may be sufficient 

 during the period of syncope to embarrass an unsound heart beyond 

 recovery. 



To employ a gasometer with the ethyl chloride vapour mixed with air in 

 the proportions required by the anaesthetist would be the most rational 

 method of administration. The necessity of carrying a large bag for this 

 purpose would, however, rob this anaesthetic to some extent of one of its 

 advantages, viz., portability. The administration is rendered less safe by the 

 employment of any apparatus for its administration in which the anaesthetic 

 is sprayed or poured into the instrument between the face piece and the bag, 

 so that during inspiration excessively high degrees of concentration of ethyl 

 chloride vapour may be given. The anaesthetic should at least be allowed to 

 mix with the air by being introduced at the end of the bag. 



I acknowledge with much gratitude my indebtedness to Professor Osborne 

 for his generous hospitality and assistance and for the use of his laboratory 

 during the course of this investigation. 



[Note by Dr. C. J. Martin. — Since Dr. Embley's paper was communicated 



