SS'S EXPERIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES. 



jar, and, when the animal falls unconscious, the air it then 

 respires is much more heavily charged with the vapour than 

 that which it breathed while still erect. On account of the 

 density of chloroform vapour, anaesthesia is more quickly pro- 

 duced when the bell-jar has an opening at the top which can be 

 plugged with cotton-wool saturated with chloroform, than when 

 the sponge is laid at the bottom of the jar ; as in the former 

 case, the vapour falling down is more rapidly diffused through 

 the air of the jar than in the latter. Instead of a bell-jar a 

 deep milk pan may be used, the rabbit or cat being placed in it 

 and the top covered by a towel stretched tightly over it. The 

 chloroform is sprinkled on the towel. Anaesthesia is thus 

 rapidly induced, but care must be taken not to allow the animal 

 to remain too long in the vessel. For large dogs an inverted 

 packing-case, without the lid, may be used instead of a 

 bell-jar. 



After the animals have been rendered insensible and the 

 operation has been begun, the anaesthesia may be kept up by 

 putting a piece of cloth round the animal's nose and pouring 

 chloroform upon it, a drop or two at a time, as often as is neces- 

 sary. In this way less chloroform is required, and there is not 

 so much danger of killing the animal by giving it the vapour 

 in too concentrated a form. 



Instead of keeping up the anaesthesia by the continued ad- 

 ministration of chloroform, it is often more convenient to open 

 a vein and inject opium or chloral. 



In operations on the abdominal viscera in dogs, e.g., in making 

 a gastric fistula, death sometimes occurs from shock, although the 

 animals are completely under the influence of chloroform. For 

 such operations ether is preferable, as it increases rather than 

 diminishes the power of the heart. If given in the same way 

 as chloroform, however, much time and a very large quantity of 

 ether are required to produce anaesthesia. Professor Schiff has 

 found,* however, that it can be readily done by pouring a 

 quantity of ether into a bladder, and holding this tightly around 

 the dog's muzzle, so that it respires ether vapour almost pure. 

 As dogs do not like to be tied down, the muzzle shown at fig. 127, 



* Professor SchifE, verbal communicatioii to the author. 



