THE PAINLESS EXTINCTION OF LIFE. 



649 



be filled and emptied through these doors with great rapidity. In 

 order to hold as many animals as possible without discomfort to them, 

 the cage is divided into two divisions or tiers, the flooring of the upper 

 tier being freely perforated with openings, so as to establish a com- 



FiG. 4.— The Cage. 



munication between the upper and lower divisions, and allow a due 

 distribution of the gases and vapors used. The cage runs on four 

 eight-inch wheels, which are underneath it, and ply on galvanized 

 iron rails. 



The mode of death to which the animals are subject is that by 

 anesthesia, not by suffocation or asphyxia. Physiologically, there is 

 a distinctive difference between these modes of death. Death by anaes- 

 thesia is death by sleep ; death by asphyxia is death by deprivation of 

 air. Death by anaesthesia is typically represented in death by chloro- 

 form ; death by asphyxia is typically represented in drowning, or in 

 immersion in carbonic-acid gas. When properly cari'ied out, death by 

 anassthesia is by far the most certain and least violent of the two pro- 

 cesses, although both are probably painless. It is worthy of record, 

 however, that all animals are not equally susceptible to the action of 

 the narcotic vapors. Cats, for instance, lie asleep much longer than 

 dogs before they cease to breathe. They fall into sleep as rapidly as 

 dogs, but do not pass so quickly into the final sleep. There is a differ- 

 ence between different animals of the same kind. Some dogs die 

 almost instantly — in fact, as they fall asleep ; others fall asleep and 

 continue to sleep for several minutes before they cease to live. In the 

 first observations, before I had rendered the narcotic atmosphere over- 

 poweringly active for all cases, there were a few instances, nine in the 

 first seven hundred, in which the animals slept on from half an hour 

 until an hour after all their comrades had died. Finding out this 

 strange peculiarity, I increased the amount of narcotic vapor until all 

 succumbed very nearly at the same minute, and in the last six thou- 

 sand there has been no recurrence of the prolonged insensibility. 

 The animals are now commonly all asleep in from two to three 



