340 ANIMAL HEAT. 



surrounded by another, which is of such dimensions that the 

 external surface of the former is separated from the internal 

 surface of the latter by a space of an inch and a half in every 

 direction. This space contains water the weight of which can 

 be readily known. The inner box can be fixed into its place 

 by a simple mechanical arrangement. The water-chamber (B) 

 is contained in a wooden case (C), which however is so large 

 that a considerable space intervenes, which is closely packed 

 with tow, the purpose of which is to prevent loss or gain of 

 heat by radiation or conduction, and thus to render the tem- 

 perature of the interior of the apparatus entirely independent 

 of that of the surrounding media. For the same reason the 

 external surface of the water-chamber is of bright tinplate. 

 The interior of the water-chamber is japanned. The zinc inner 

 chamber for the reception of the animal is left as it is. 



The temperature of the animal having been measured by 

 passing a thermometer an inch and a half into the rectum, it 

 is placed in the box, the exit tube of which has been previously 

 brought into communication with an aspirator. The lid is then 

 rapidly but carefulty closed with putty, and the whole placed 

 without loss of time in the water-chamber. The water-chamber 

 is then closed and immediately covered with a layer of tow. 

 In its lid there are two oblong openings for the introduction 

 of stirrers. 1 The water having been agitated immediately 

 after the introduction of the box containing the animal, a 

 thermometer is introduced by one of the openings already 

 mentioned, which after three minutes is read. The time having 

 been noted, the apparatus is left to itself for fifteen minutes, 

 half an hour, or an hour, and the temperature is again ob- 

 served after agitation of the water. The results having been 

 noted, the animal is withdrawn with as little delay as possible 

 from the case containing it, and the thermometer is introduced 

 into the rectum to the same distance as before, and read after 

 the same interval of time. 



In this way obviously four readings are obtained those of 

 the animal and of the calorimeter at the beginning and end of 

 the given period. To interpret them we must take into ac- 

 count, not only the relative weights of the animal and of the 

 calorimeter, but their several capacities for heat. In the case 

 in which the temperature of the animal remains the same, the 

 amount of production being equal to that of discharge, all 

 that is required is to know how much heat has been communi- 

 cated during the period of observation to the calorimeter. In 

 the opposite case we must, in order to judge of the quantity 



1 I have lately adopted a better method of agitation, consisting in the 

 injection of air into the space below the chamber A. The construction 

 is such that the whole of the air so used finds its way into the chamber. 



