346 



A MANUAL OF VETERINARY PHYSIOLOGY 



The animal is enclosed within three sealed walls, each separated 

 by an air space, the inner one being the calorimeter. Food for the 

 period is supplied by a specially arranged door, the excreta col- 

 lected, and the heat of the chambers registered. The heat is absorbed 

 by a current of cold water passing through copper pipes at the top 

 of the respiration chamber ; . . . the temperature of the ingoing 

 and outcoming water is read every four minutes by means of two 

 thermometers graduated to jfo° C. The inner wall of the chamber 

 is copper and zinc, with a 3 -inch dead space between each metal ; 

 these are connected by 600 couples connected in series, with a 

 reflecting galvanometer, serving to indicate any difference in tem- 

 perature between the inner and outer surface. Special arrangements 

 exist for heating or cooling this air space so as to rectify any differ- 

 ence which may exist. The temperature of the chamber is registered 

 by means of a series of copper resistance thermometers, connected to 

 a slide wire Wheatstone bridge. All the heat evolved by the animal 

 must leave the apparatus either as sensible heat in the water 

 current, or as latent heat of water vapour. So delicate is the 

 apparatus that corrections have to be made for the heat arising from 

 the friction of water in the coil of copper pipes. 



The respiratory portion of the apparatus is furnished with a 

 special form of pump which can be graduated to deliver a given 

 number of litres of air per minute ; the same pump is regulated to 

 deliver a given quantity of air at special intervals for analysis. 

 Another pump draws this air through the special apparatus, which 

 determines the water and C0 2 , after which it passes through appli- 

 ances where the combustible gases are determined. The plan of 

 this apparatus is seen in Fig. 105, while the general arrangements 

 outside the chamber for its efficient working are seen in Fig. 106. 



The following example of a balance experiment — viz., the 

 amount of nitrogen and carbon received and got rid of — was per- 

 formed with the above apparatus. The animal was a steer. 

 The rations consisted of 4,531 grammes (9-9 pounds) hay and 

 400 grammes (o-88 pound) linseed-meal. 



The hay contained 

 The linseed - meal con- 

 tained - 

 The faeces contained 

 The urine contained 

 The hair, etc., contained 

 The carbon dioxide con- | 

 tained - - - 1 

 The methane contained 

 Lost by body - - 



Nitrogen. 



Carbon. 



53'8 53'8 



735" 2 



1735*2 



