LECTURE XXI. 



Of the feeding of animals, and the purposes served by their food.-~Substances of which the 

 parts of animal bodies consist. — Whence do the animals derive these substances— are 

 they all present in the food? — Use of the starch, gum. and sugar contained in vegetable 

 food.— Functions of a full-grown animal. — Of the respiration of animals. — General origin 

 and purposes served by the fat in carnivorous an 1 herbivorous animals.— Of the digestive 

 process in animals. — Purposes served by food and digestion. — The food sustains the full- 

 grown animal. — Necessity of a mixed food. — It sustains and increases the fattening ani- 

 mal. — Relative fattening powers of different kinds of fooii.— How circumstances affect this 

 fattening property.— Purposes served by food in the pregnant — in the yonng and growing 

 animals, such as the calf— and in the milk cow. — Effect of different kinds of food on the 

 quality of the milk. — Fattening of the cow as the milk lessens in quantity — Experimental, 

 economical, and theoretical value of different kinds of food for these several purposes. — 

 Circumstances which affect these values. — Soil, manure, form in which the food is given, 

 ventilation, light, warmth, exeicise, activity, salt and other condiments. 



Having in the preceding lectures considered tlie composition of the 

 direct products of the soil — grains, roots, ana grasses — and of the most 

 important indirect products — milk, butter, and cheese — the only part of 

 our .subject which now remains to be discussed is the relative values of 

 these several products in the feeding of animals. 



Under this head it will be necessary to enquire how far these values 

 are affected by the age, the growth, the constitution, and race of the ani- 

 mal — by the purposes for which it is fed — and by the circumstances 

 under which it is placed while the food is administered to it. 



§ 1. O/* the substance of which the parts of animals consist. 



The bodies of animals consist of solid and fluid parts. 

 1°. The solid parts are chiefly made up of the muscles, the fat, and 

 the bones. 



a. The muscles^ in their natural state, as I have already had occasion 

 to mention (p. 444), consist in 100 parts of about — 



Dry matter 23 



Water 77 



100 

 so that, to add 100 lbs. to the weight of an animal in the form of muscle, 

 only 23 lbs. of solid matter require to be incorporated with its system. 



When the muscular or lean part of beef, mutton, &c., is wa.shed 

 in a current of water for a length of time — the blood, to which the red 

 colour is owing, and all the soluble substances, gradually disappear, and 

 the muscle becomes perfectly white. In this state, with the exception 

 of some fatty and other matters which still remain intermixed with it, the 

 white mass forms what is known to chemists by the name of fibrin. 

 This name is given to it because it forms the fibres which run along the 

 muscles and constitute the greater portion of their substance. 



The following table exhibits the relative proportions of muscular fibre 

 and other substances contained in the flesh of several different animals in 

 its natural .state, [Schlossberger, Annalen der Pharmacie, December, 

 1842, p. 344] :— 



