THE PAINLESS EXTINCTION OF LIFE. 645 



it was cooled without any other artificial means, so as never to raise the 

 chamber above summer heat ; it was produced cheaply ; and it afforded 

 such simple action that any workman could at once learn to use it. 

 Another useful result springing from the employment of this stove 

 was, that it enabled me to diffuse other narcotics into the chamber, by 

 merely allowing the warm gas proceeding from the stove to pass over 

 a porous surface, charged with the narcotics, on its way into the 

 chamber. 



To apply the narcotic gas or vapor, it is necessary to have a closed 

 place in which the animals are exposed to the narcotic, and another 

 place in which they are collected preparatory to being subjected to the 

 narcotism. This implies what I have called the lethal chamber, and a 

 cage. At Battersea, it was necessary to have an apparatus large 

 enough to narcotize as many as one hundred dogs at a time. It was, 

 therefore, essential to have a large lethal chamber, and one that was 

 strong and effectively constructed. I noted down at the beginning 

 the following requirements, all of which I had calculated out of a 

 series of preliminary studies, and cbnstructed on a small working scale. 



1. The chamber, of whatever substance built, must be so con- 

 structed that its interior shall not be subject to great variations of 

 temperature. This I knew to be very important, since, in observing 

 the action of narcotic vapors on the human subject, I had learned that 

 humidity and cold materially interfere with their quick action, while 

 dryness and warmth favor such action. In a lethal receptacle, such as 

 was being constructed, there could be no certainty whatever, unless 

 the temperature and dryness were at all times uniform. 



2. It was necessary so to construct the chamber that sufficient but 

 not an excess of room should be allowed in it for the expansion of the 

 gases introduced. It might seem at first sight, and before inquiry 

 was instituted, that the more the space within the chamber was re- 

 duced the quicker would be the effect. This, however, is not practi- 

 cally the fact. In order to secure perfect diffusion of the narcotic 

 atmosphere, the space to be filled with it must be about one eighth 

 greater than is absolutely required for a cage, fully charged with the 

 animals that have to be killed. 



3. Much care is required in connecting the stove with the chamber, 

 so as to make sure of equal diffusion of the gases or vapors through 

 the inclosed space. Unless this equal diffusion is rendered effective, 

 some of the animals are more exposed to the vapors than others, and 

 the effects are irregular, which is as bad a result as could possibly be 

 obtained. 



4. It was essential to provide that a sufficient quantity of the nar- 

 cotic should be introduced before and for a brief period after the 

 introduction of the animals. 



5. It was requisite to invent a plan by which the chamber could be 

 kept completely closed until the precise moment when the animals 



