MEAT PRODUCTION 455 



be approximately proportional to their body surface (345), 

 and there is even good ground for believing that this law applies 

 in a broad way to animals of the most diverse species and size. 

 Since the action of external temperature is also approximately 

 proportional to the surface, it would be expected that the size 

 of the animal would not be an important factor. In fact, however, 

 the other conditions are rarely alike. The young animal in 

 particular is likely to be getting a relatively lighter ration than 

 the animal which is being pushed for the butcher, and thus to 

 have less surplus heat at its disposal, while the indefinable factor 

 of " hardiness " would also seem to be in favor of the older 

 animal. 



539. Humidity. The relative humidity of the air is an im- 

 portant factor in the temperature relations of the animal. 

 Moist air tends to increase the conductivity of the hair or wool, 

 just as it does that of the clothing of man, thus facilitating the 

 escape of heat and raising the critical temperature. Accord- 

 ingly, it is to be anticipated that in a dry climate, like that of 

 the northwestern United States, animals might be safely exposed 

 to a greater degree of cold than in a damp climate, like the 

 winter of the seaboard States. 



540. Temperature of drinking water. In general, the 

 same considerations adduced in discussing the influence of the 

 temperature of the air apply to that of the drinking water. 

 Under heavy feeding, especially, unless in very cold quarters, 

 the animal has a surplus of heat which it can apply to warming 

 its drink. If, then, the latter is at such a temperature as to be 

 consumed freely, there would seem to be no occasion for heating 

 it further, except for one important consideration. The tem- 

 perature of the air acts continuously and with approximate 

 uniformity. That of the water, on the other hand, acts only 

 at intervals, often only two or three times or even once per day. 

 If, now, the animal consumes within a short time a large amount 

 of cold water, a correspondingly rapid expenditure of heat is 

 required to warm this water to the body temperature, and this 

 demand may for a time exceed the supply of surplus heat and 

 cause an increased oxidation of tissue or food material for the 

 sake of heat production only. Such a loss can never be made 

 good at a later hour since, once converted into heat, the energy 

 has escaped from the grasp of the body. Other things being 



