185' 



NEW ENGLAND FARMER. 



371 



FEEDING OF ANIMALS. 



On the feeding of animals. — Main visible functions of th; living 

 animal. — The food must supply the wants of respiration. — 

 Nature, wants, and purposes of this function. — The daily 

 waste of the muscular parts and tissues of the body. — Food 

 necessary to repair it. — Saline and earthy matters containeil 

 in its several parts, and daily rejected by the body. — Waste or 

 increase of fat supplied by the food. — Special waste in the per- 

 spiration. — Forms in which the solid matter of the tissues es- 

 cape in the urine of animals. — General balance of food and 

 excretions. — Kind of food required, as indicated by the com- 

 position of the blood. — Importance of a mixed food. 



The food of plants ^ve have seen to consist es- 

 sentially of two kinds, the organic and the ino?-- 

 ganic, both of which are e<iually necessary to the 

 living vegetable — equally indispensable to its 

 healthy gi-owth. A glance at the purposes served 

 by plants in the feeding of animals, not only con- 

 firms this view, but throws also additional light 

 upon the hind of inorganic food which plants must 

 bo able to procure, in order that tliey may be fit- 

 ted to fulfil their assigned purpose in the economy 

 of nature. 



MAIN VISIBLE FUNCTIONS OF LIVING ANIM.VLS. 



Man, and all domestic animals, may bo sup- 

 ported, may even l)e fattened, upon vegetable food 

 alone. Vegetables, therefore, must contain all 

 the substances which are necessary to luiild up 

 the several parts of animal bodies, and to supply 

 the waste attendant upon the performance of the 

 necessary functions of animal life. 



All living animals perform tliree main or lead- 

 ing functions necessary to the continuance of 

 healthy life. 



1. They breathe, alternately inhaling and ex- 

 haling air by means of the lungs. 



2. They digest, dis.so]ving the food in the sto- 

 mach, and selecting from it the materials neces- 

 sary to form blood. 



3. They excrete, rejecting in the solid excre- 

 tions and the urine, or giving off from the skin 

 and the lungs — 



a. That part of the food which cannot be dis- 

 solved and made use of as it passes tlirough the 

 alimentary canal. 



b. The materials derived from tlio decomposed 

 tissues or parts of the body which are undergoing 

 a constan'u waste. 



To the wants of an animal perfurming these 

 visible functions in a healthy and roguLiv manner, 

 the food must be adapted in kind and ipiantity. 

 I shall briefly illustrate what these wants de- 

 mand. 



To the numerous minor and invisiblo functions 

 performed within the several parts of the living 

 body, it is unnecessary to advert in detail. 1 may 

 have occasion incidentally to advert to one or two 

 of the more interesting of these; but as a healthy 

 blood contains all that is necessary to the dis- 

 charge of these functions, it would only compli- 

 cate our present inquiry to consider their several 

 direct relations to the undigested food as it is in 

 troduoed to the stomach. 



IDE FOOD MUST SUFPLY THE WANTS OF RESPIRA- 

 TION. — NATURE, WANTS, AND PURPOSES OF 

 THIS FUNCTION. 



While an animal lives it breathes. It alter 

 nately draws in and throws out atmospheric air 

 by means of its lungs. 



1. When tliis air enters, it contains about two 

 gallons of carbonic acid in every 5000; when ites 

 capes from the lungs it contains 2 gallons or up 



wards in every 100. The proportion is increased 

 from 50 to 100 times. Much carbonic acid, there- 

 fore, is given ofT from the lungs of animals dur- 

 ing breathing. In other words, living animals 

 are continually tlu'owing off carbon into the air, 

 since carbonic acid contains about two-sevenths of 

 its weight of solid carbon. 



A man of sedentary habits, or whose occupation 

 requires little bodily exertion, may throw off in 

 this way about five ounces of carbon in twenty- 

 four hours-one who takes moderate exercise, about 

 8 ounces — and one who has to undergo violent 

 bodily exertion, from 12 to 15 ounces. In our 

 climate about one-fifth more is given off in sum- 

 mer than in winter. 



If we take the mean quantity respired at 8 

 ounces, then, to supply this carbon alone, a man 

 must eat 18 ouncesof starch and sugar every day.* 

 If he take it in the form of wheaten bread, he will 

 require V\ lb. of bread ; if in the form of potatoes, 

 about 7i lbs. of raw potatoes to supply the carbon 

 which escapes through his respiratory organs 

 alone. 



When the habits are sedentary, 5 lbs. of pota- 

 toes may be sufficient; when violent and continued 

 exercise is taken, 12 to 15 lbs. ma}!- be too little. 

 At the same lirae, it must be observed that when 

 the supply is less, either the quantit}' of carbon 

 given off will be less also, or the deficiency will be 

 supplied at the expense of the body itself, especi- 

 ally its fatty part. In either case the strength 

 will be impaired, and increased supplies of nour- 

 isliing food will be required to recruit the exhaust- 

 ed frame. 



Other animals give oil' from their lungs ciuanti- 

 ties of carbon proportioned to their weights. A 

 cow or a horse, eiglit or ten times the weight of a 

 man, will give oft'4 to 5 lbs. of carbon. The quan- 

 tity of food required to supply this carbon will be 

 proportionably greater. 



1 have in the above calculations supposed that 

 the whole of the carbon given off from the lungs 

 is derived from tlio starch, sugar, or gum of ^the 

 food. This view is the simplest, and most easily 

 intelligible. It only requires us to suppose that 

 in the system the starch is separated into carbon 

 and water, of which, as we have seen, (p. 43,) it 

 may be represented to consist ; and that the former 

 is given or burned off from the lungs in the form 

 of carbonic acid. But many physiologists do not 

 regard the process as being really so very simple. 

 They consider tliat the carbon given oil' is partly 

 derived from the gluten or flesh of the food, as 

 well as from the starch or fit — in which case the 

 quantity of starch or sugar in tlio food, as T have 

 calculated it, need not be so large; and it is cer- 

 tain that where animals live on food which con- 

 tains no starch or sugar, and but little fat, the 

 gluten or fleshy fil)re it contains must yield the 

 carbon whicli is given off by the lungs. 



2. But when the air escapes from the mouth of 

 a breathing animal, it contains mucli moisture 

 also. It enters comparatively dry, it comes out 

 so moist as readily to deposit dew upon any cold 

 surface, or to form a white mist in a wintry at- 

 mosphere. This water is given off by tiio lungs, 

 along with the carbonic acid, and, like it, is de- 

 rived from tlic food, solid or liquid, which has 

 been introduced into the stomach. It may cither 

 be part of the water which has been swallowed 

 as such, or the water which may be supposed to 



