264 EXPERIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES. 



less, accoidbg to the size of the frog), and then suddenly pres- 

 sing it down on a metal plate, so that a broad rim is formed 

 round the end. The sides of the larynx are seized by two 

 artery forceps, the cannula introduced, and tied firmly in. A 

 Richardson's spray-producer, from which the tubes have been 

 removed, is then connected with it and used as a bellows. 



Introduction of Gases or Vapours into the Lungs. — Gases or 

 vapours may be introduced into the lungs eitlier by simple 

 inhalation or by artificial respiration. For the inhalation of a 

 gas, a conical bag of oilskin, india-rubber, or bladder, must be 

 made to fit the snout of the animal, and connected with a bag, 

 bladder, or gas-holder containing the gas. Or a tube may be 

 put into the trachea and connected wdth the gas-holder. 



For the inhalation of a vapour, a cone of strong paper or 

 cardboard may be used, the wide end being put over the muzzle, 

 and the liquid, the vapour of which is to be inhaled, dropped on 

 a piece of blotting-paper and put on the small end. Or the 

 whole cone may be made of blotting-paper. 



Many different kinds of apparatus have been used for the 

 artificial respiration of gases, among which may be men- 

 tioned the ingenious instrument of Thiry and the beautiful 

 respiration-pump of Ludwig. The simplest method probably is 

 to have the gas in a bag, connected by means of the bottle or 

 Mtiller's valve witli the tracheal cannula. The gas may then 

 be forced into the lung at intervals, by alternately compressing 

 and relaxing the bag. 



Air may be loaded with the vapour of any kind of fluid before 

 it is sent into the lungs, either by mixing the fluid with the 

 water in the bottle-valve, or by emptying out the water and 

 putting a little of the fluid alone on the bottom of the bottle. 

 Pure air or air loaded with vapour may be sent into the lungs 

 alternately by the arrangement shown in Fig. 130. A stream of 

 air is sent from the bellows through the india-rubber tube s, 

 and divided into two by the T-tube t'. When the clip x is 

 removed, and x' put on, the air passes straight through to the 

 tracheal cannula z. If x be now put on, and x' removed, the 

 air passes through v (Miiller's valve), and becomes loaded with 

 the vapour of any fluid placed in the bottle. 



