CONSTITUENTS OF FOOD. 101 



will be drawn from the tissues, a portion of which will on that 

 account become broken down. These untoward results will 

 occur only when the quantity of salt which has been consumed 

 is very large ; for with a plentiful supply of drinking water, the 

 kidneys rapidly eliminate salt from the system. 



The amount of soda in soil varies greatly, and consequently 

 the percentage of soda in plants and also in the animal body 

 is of too variable a nature to permit of our making exact 

 calculations for determining the amount of salt which should 

 be added to a horse's food, so as to adjust the proportion 

 which the soda should bear to the potash. We may, how- 

 ever, base an approximate calculation on their proportion 

 in milk, namely, about 2^ parts of potash to I part of 

 soda. Take, for instance, the case of meadow hay, which, 

 according to Warington (Chemistry of the Farm), contains 28.8 

 oz. of potash and 5.21 oz. of soda in every 100 Ib. Here the 

 proper amount of soda, taking milk as a standard, should be 

 11.52 oz. ; the deficiency being consequently 6.31 oz., which is 

 made up of 4.68 oz. of sodium and 1.63 oz. of oxygen. To 

 supply the missing 4.68 oz. of sodium by means of common 

 salt (sodium chloride), we shall require 11.9 oz. (say 12 oz.) of 

 that mineral. Supposing, therefore, that we give a horse an 

 inclusive daily ration of 30 Ib. of meadow hay, we ought to add 

 to it about 3^ oz. of common salt ; or at least I oz. for every 

 lolb. of meadow hay. Church (Food Grains of India) tells us 

 that " the due admixture of food-grains belonging to different 

 classes will secure the necessary mineral ingredients, provided 

 an allowance of at least 230 grains of common salt be added 

 to the daily ration of a man having a body weight of 105 Ib." 

 This would be equivalent to about 5 oz. for a horse weighing 

 1,000 Ib. Church also states that " the amount of salt con- 

 sumed per head per day in the Bombay Presidency just 

 exceeds j oz. ; in Sind it is calculated to be a little more 

 than oz." I draw attention to these Indian statistics, 



