I06 AGRICULTURAL RESEARCH AND THE FARMER! 



of water flows. The whole tank is surrounded by 12 inches of 

 granulated cork to prevent as far as possible loss of heat to the 

 surrounding air — with the exception of the door, which is insu- 

 lated with felt. The water which flows through the spiral pipe 

 enters at a temperature which is kept constant by an electric 

 thermostat. If there is an animal in the calorimeter, the circu- 

 lating water picks up the heat given off by the animal and is thereby 

 warmed. The differences in temperature between the outflowing 

 and inflowing water, expressed in Centigrade degrees, multiplied 

 by the number of litres flowing round the calorimeter in, say, 

 one minute, gives the amount of heat (in calories) extracted 

 during that minute. To this must be added corrections for heat 

 carried out or in by the ventilating air, the latent heat in the water 

 vapour given off by the animal, and leakage of heat through the 

 walls of the calorimeter. The sum of these gives the heat given 

 out by the animal per minute. 



The calorimeter — which has only recently been completed — 

 is being used for some preliminary experiments on the nutrition 

 of the pig. When this work is completed it is proposed to begin 

 an investigation of the net nutritive value of various feeding stuffs, 

 to ascertain how much of the value of various foods is lost in the 

 processes of digestion and utilisation. 



It is not contended that the Cambridge calorimeter will give 

 absolutely accurate records. To secure them, a very much more 

 expensive apparatus would be required. Existing calorimeters 

 in America and elsewhere give extremely accurate results, but 

 they cost some thousands of pounds to erect and require an 

 expert staff of half-a-dozen or more attendants to conduct an 

 experiment. Funds for research are much more readily forth- 

 coming in America, however, than in this country, and the 

 Cambridge apparatus — which could be duplicated for less than 

 ;^500 and is easily worked by one person — represents a commend- 

 able attempt to do the best that is possible under existing financial 

 conditions in England, and will, it is confidently believed, prove 

 a very valuable means of adding to our present store of informa- 

 tion regarding animal nutrition. 



A still cheaper apparatus has been devised by the Aberdeen 

 Institute. This apparatus is a modification of tl.' Haldane 

 Douglas method already employed in connection with nutrition 

 experiments on the human subject, and can be marlf at a cost of 

 about £25. The consumption of oxygen and the oduction of 

 carbon dioxide and methane by an animal can be determined, and 

 from these data it is possible to calculate the production of 

 energy by an animal under different conditions, and also to get 

 an indication of the use made of the constituents of the food 



