RESEARCHES ON CHLOROFORM ANAESTHESIA 643 



it is exceedingly rare not to see this effect on a respiratory 

 tracing. Any individual animal may exhibit this phenomenon 

 in different degrees, and cessation of respiration may be per- 

 manent unless resort is had to some means of artificial respira- 

 tion. Still more interesting is the fact that when the same 

 animal is anaesthetised several times with the same per- 

 centage of chloroform vapour, this condition, which may be 

 considered to indicate the first danger point in chloroform 

 anaesthesia, occurs at the same time, and presents a constant 

 type of impaired respiration. During this early period, in 

 about two to three minutes after the administration of chloro- 

 form has commenced, a veritable danger point exists, and an 

 elementary account of the physiology of this will be briefly 

 described. 



Nicloux points out that during this pre-anaesthetic period 

 the intake of chloroform is rapid even with a low percentage 

 of chloroform in the inspired air. Thus, within three minutes, 

 56 mgrs. per cent., an amount not much below the lethal 

 quantity, were found in arterial blood when a somewhat large 

 amount of the anaesthetic was supplied. Mansion and Tissot 

 found that when a 4 per cent, chloroform-air mixture is inhaled, 

 arterial blood becomes slowly but steadily charged with chloro- 

 form until the content of the drug in the blood is almost 

 identical with the amount of vapour which it can hold in vitro. 

 This is about 45 mgr, per 100 grammes of blood for an 

 atmosphere containing 4 per cent, of chloroform (Tissot). After 

 administration of this strength of chloroform, arterial blood 

 contained the following amounts : 



After . . I hr. 42 m. i hr. 50 m. 5 hrs. 15 m. 6 hrs. 56 m. 8 hrs. 21 m. 

 Mgrs. CHCI3 27 30-5 367 42-4 46-2 



In the experiments of Brodie and Widdows ^ the rate of 

 absorption of chloroform during the introduction of anaesthesia 

 was ascertained by allowing animals to inhale a known 

 percentage strength of chloroform vapour, i •06-278 per cent. 

 Both the volume of air expired during any interval of time 

 and the percentage of chloroform in this were determined, 

 the latter by the same method which Vernon Harcourt had 

 adopted, which depended upon the combustion of chloroform 



^ Brit. Med, Joiirtial^ July 14, 1906. 



