444 Mr. J. S. R. Russell. Circumstances under which [May 18, 



II. The Effects of the Inhalation of Certain Gases. 



1. Nitrogen. — As has been already noted, a T'fa^e. was made use 

 of in these experiments ; one limb of the "]~ being connected with the 

 tracheotomy tube, one by means of india-rubber tubing, with the gas 

 reservoir, and one being left free with a small piece of india-rubber 

 tubing fitted on to its extremity. The tube leading from the gas 

 reservoir was grasped between the fingers and thumb of one hand, 

 while the piece of tube at the extremity of the free limb of the "J" 

 was grasped between the fingers and thumb of the other hand. 

 During inspiration the free end was closed, while the tube from the 

 bag of nitrogen was left free, and during expiration the tube from the 

 nitrogen was closed, and that opening into the air of the room was 

 opened. In this way nitrogen gas was alone inspired, while expira- 

 tion took place into the air of the room. 



Except that it took a longer time to obtain the results, the effects 

 were identical with those met with in asphyxia.* The loss of knee jerk 

 was preceded by the stage of exaltation, and when the animal was 

 allowed to recover the absence of knee jerk was followed by a stage 

 of slighter exaltation before its return to the normal state, such as 

 existed before the administration of the nitrogen. 



2. Nitrous Oxide. — The plan of procedure was the same in these 

 experiments as in the last, and the results differed from them in no 

 way. Loss of the knee jerk was always preceded by a stage of exalta- 

 tion, and when the animal was allowed to recover, the normal state of 

 the knee jerk was only reached after passing through a period during 

 which it was exalted. 



3. Oxygen. — Here again the plan of procedure was the same as in 

 the experiments with nitrogen ; bat the results were widely different. 

 Indeed, they were totally different from any that had been previously 

 obtained, for in no case was the knee jerk abolished, no matter how 

 long the so-called apnceic state was kept up. Increased activity of 

 the knee jerk, gradually becoming more so until clonus developed, 

 was the only effect of inhalation of this gas. When its administra- 

 tion was discontinued the knee jerk gradually returned to the condi- 

 tion in which it was before the inhalation of oxygen was commenced. 



III. The Action of Ancesthetic Agents. 



1. Ether. — In profound narcosis induced by the inhalation of ether 

 the knee jerk is abolished ; but this stage is preceded by one of in- 

 creased activity, and followed by a similar stage of exaltation when 

 the animal is recovering from the effects of the anaesthetic, and before 

 the knee jerk returns to its normal conditions. The length of time 



* Cf. Martin, ' Journ. of Physiol.' J 



