The fact that food contains albuminoids, which correspond to the constituents of flesh, and hydrocarbons, which represent fats, and also mineral constituents, which have been referred to, has led physiologists to adopt certain theories in reference to the function of each class of food in the animal body. The nitrogenous constituents and albuminoids have had ascribed to them the function of flesh-formers. They are distinguished from other nitrogenous constituents by the presence of a small quantity of sulphur and phosphorus, which constituents are absent from gelatine. Fats and also carbohydrates, such as starch and sugar, are considered to represent the combustible materials or heat-forming substances which are consumed in the process of respiration, the excess being deposited in the form of fat.

It is stated that animals cannot subsist on a diet composed exclusively of flesh-forming materials, nor on one from which carbohydrates are entirely excluded. On the other side there are instances recorded of animals having lived in perfect health for a considerable time on nitrogenous and also on non-nitrogenous foods. These exceptional cases need not be taken into account in practice, as there is sufficient evidence that the animal to-day requires for its support a food in which are combined all the constituents which are found in the organism.

Experiments have shown that nitrogenous food can be used for the formation of fat, and it is admitted that all the fat which is found in the body could not have been obtained from the amount of fatty matters which have been consumed as food. And the fact of animals having lived and been maintained in health on purely nitrogenous diet, is sufficient in itself to show that a considerable proportion of the material must have been consumed in the process of respiration.

Assuming that albuminoids are chiefly concerned in the formation of flesh and the development of force, only contributing in a minor degree to the formation of fat, it must also be allowed that fats have for their principal function the production of heat as a result of oxidation, and in this they are assisted by other carbohydrates - starch, sugar, and gums. But it is certain that they do not in any way contribute to the formation of nitrogenous constituents.

An important point is to be considered in reference to the respective value of each article of diet and its digestibility. A food may contain a considerable proportion of albuminoids which are comparatively useless to certain animals, on account of the digestive organs being incapable of appropriating the nutriment they afford. Bean straw, for example, contains 8 per cent of nitrogenous substances, but its structure renders it comparatively indigestible as food for the horse, in which animal digestion is quickly performed, while it may be valuable diet for cattle, with their prolonged process of digestion, including rumination, which is really remastication. The following table from Warington's Chemistry of the Farm indicates the amount of water, nitrogenous substances, fat, soluble carbohydrates (starch, sugar, gums), fibre, ash, and albuminoids in the foods which constitute the provender of farm animals, and most of these foods are employed for feeding horses: .

Percentage Composition Of Ordinary Foods

Food.

Water.

Nitrogenous Substance.

Fat.

Soluble Carbohydrates.

Fibre.

Ash.

Albuminoids.

Amides, etc.

Cotton Cake (decorticated)

8.2

43.2

1.8

13.5

20.8

5.5

7.0

Cotton Cake (undecort.) ...

12.5

20.7

1.3

5.5

34.8

20.0

5.2

Linseed Cake

11.7

26.9

1.1

11.4

33.2

9.0

6.7

Rape Cake ...

10.4

28.1

4.6

9.8

29.1

10.3

7.7

Earthnut Cake

11.5

45.1

1.9

8.3

23.1

5.2

4.9

Beans

14.3

226

2.8

1.5

48.5

7.1

3.2

Peas

14.0

20.0

2.5

1.6

53.7

5.4

2.8

Wheat

13.4

10.7

1.3

1.9

69.0

1.9

1.8

Rye .........

13.4

10.5

1.0

1.7

69.5

1.9

2.0

Oats

13.0

10.6

0.7

5.4

57.3

10.0

3.0

Barley

14.3

10.2

0.4

2.1

66.0

4.5

2.5

Maize

11.0

9.8

0.6

5.1

70.0

2.0

1.5

Malt Sprouts

10.0

16.6

7.1

2.2

44.1

12.5

7.5

Wheat Bran

13.2

12.1

2.0

3.7

56.0

7.2

5.8

Brewers' Grains

76.2

4.9

0.2

1.7

10.7

5.1

1.2

Brewers'Grains (dried) ...

9.5

19.8

0.8

7.0

42.3

15.9

4.7

Rice Meal ...

10.3

11.3

1.0

12.0

47.8

8.6

9.0

Oat Straw ...

14.5

3.5

0.5

2.0

37.0

36.8

5.7

Barley Straw

14.2

3.2

0.3

1.5

39.1

36.0

5.7

Wheat Straw

13.6

3.3

1.3

39.4

371

5 3

Pea Straw ...

13.6

9.0

1.6

33.7

35.5

6.6

Bean Straw

18.4

8.1

1.1

31.0

36.0

5.4

Pasture Grass

76.7

2.9

1.1

0.9

10.9

5.2

2.3

Clover (bloom beginning)

81.0

2.6

0.8

0.7

8.0

5.2

1.6

Clover Hay (medium)

16.0

105

2.5

2.5

37.2

25.0

6 3

Meadow Hay (best)

15.0

10.2

1.8

2.3

39.5

24.0

7.2

Meadow Hay (medium) ...

15.0

8.0

1.2

2.2

42.0

25.4

6.2

Meadow Hay (poor)

14.0

6.3

05

2.0

41.1

31.0

5.1

Grass Silage (stack)

670

3.3

1.5

1.5

13.2

9.7

3.8

Clover Silage (stack)

67.0

3.3

2.7

2.2

10.5

11.9

2.4

Maize Silage

79.1

1.0

0.7

0.8

11.0

6.0

1.4

Potatoes

75.0

1.2

0.9

0.2

21.0

0.7

10

Cabbage

85.7

1.7

0.8

0.7

7.1

2.4

1.6

Carrots

87.0

0.7

0.5

0.2

9 3

1.3

1.0

Mangels (large)

89.0

0.4

0.8

0.1

7.7

10

1.0

Mangels (small)

87.0

0.4

0.6

0.1

10.2

0.8

0.9

Swedes

89

0.7

0.7

0.2

7.2

1.1

0.8

Turnips

91.5

0.5

0.5

0.2

5.7

0.9

07 i