THE ANIMAL BODY DIGESTION METABOLISM 17 



of fatness contain less water and protein and considerably more fat 

 than cattle. The fat hog, for example, contains 43.9 per ct. fat and 

 only 11.4 per ct. protein. Due to their small skeletons, the bodies of 

 swine contain less ash than those of cattle and sheep. 



30. Mineral matter. The preceding table shows that mineral matter, 

 or ash, at no time forms a large part of the body, as it ranges from only 

 1.7 per ct. in the fat hog to 4.5 per ct. in the growing steer. Yet, as 

 will be pointed out later, mineral matter has exceedingly important func- 

 tions in the animal body. Indeed, an animal will die sooner if given 

 plenty of food, which has, however, been freed from mineral matter, 

 than if given no food at all. (95-101) 



The following table shows the principal mineral constituents in the 

 bodies of the animals (fasted live weight) analyzed by Lawes and 

 Gilbert, and also in milk and unwashed wool : 



Mineral matter in 1,000 Ibs. of farm animals, milk, and unwashed wool 



Phosphoric 



Lime acid Potash Magnesia 



(CaO) (P,0 6 ) (K 2 0) (MgO) 



Lbs. Lbs. Lbs. Lbs. 



Fat calf 16.46 15.35 2.06 0.79 



Half-fat ox 21.11 18.39 2.05 0.85 



Fat ox 17.92 15.51 .76 0.61 



Fat lamb 12.81 11.26 .66 0.52 



Sheep, before fattening 13 . 21 11 . 88 .74 . 56 



Fatsheep 11.84 10.40 .48 0.48 



Pig, before fattening 10.79 10.66 .96 0.53 



Fat pig 6.36 6.54 .38 0.32 



Milk 1.70 2.00 .70 0.20 



Unwashed wool 1.80 0.70 56.20 0.40 



Because they form the chief mineral constituents of the bones, lime 

 and phosphoric acid greatly exceed in amount the other mineral com- 

 ponents of the body. Lime, the largest mineral constituent of the bones, 

 ranges from about 6 Ibs. per 1,000 Ibs. of carcass in the fat pig to over 

 21 Ibs. in the ox. Phosphoric acid almost equals lime in quantity, while 

 there are only from 1 to 2 Ibs. of potash per 1,000 Ibs. of animal and still 

 less magnesia. Soda, silica, iron, etc., are found in small amounts. 



31. Plants and animals compared. Two fundamental differences be- 

 tween plants and animals have already been pointed out: First, that 

 the wall or membrane which surrounds the cells in the bodies of animals 

 is formed of protein, while the cell walls in plants are made of cellulose ; 

 second, that in animals most of the reserve food is stored in the form 

 of fat, while in plants reserve food is stored chiefly in the form of 

 starch. The other main difference between plants and animals is that 

 the higher plants are nourished by inorganic matter, while animals 

 must live almost entirely upon organic matter. 



Plants absorb thru their leaves great quantities of carbonic acid 

 gas, composed of carbon and oxygen, retaining the carbon and giving 

 off the oxygen as waste. Animals take free oxygen thru their lungs 



