134 THE NATURE AND TREATMENT OF 



sympathetic headache, or the stomach grows refractory, and 

 casts up the burden, for the simple reason that its function is 

 overtaxed. It must have rest. The same rule applies to the 

 muscular and mental natures. If, therefore, hard labor devel- 

 ops the function of either, rest, at suitable intervals, preserves 

 their integrity, and therefore must not be disregarded. 



In selecting food for working animals, we must remember 

 that they require certain inorganic equivalents, which seem to 

 be as necessary for the support of the system as nutriment. 



Salt, for example, is not nutritious, yet neither man nor 

 brute can long exist without it. Common salt, chloride of 

 sodium^ is decomposed in the stomach, and is there found in the 

 form of muriatic acid and soda ; the former is supposed to aid 

 digestion, and the latter eliminates bile. 



Neither is phosphorus (found in straw) nutritious, yet that 

 article is actually necessary for the support of life. It is an 

 element of both vegetable and animal organization, the former 

 absorb it from the soil, and in turn, yield it to animals for the 

 promotion of their health and longevity. It serves to develop 

 bone, muscle, and nerve. Animals require phosphorus just as 

 much as they do meal and oats ; the former is decidedly nu- 

 tritious, yet deficient in phosphoric acid. 



Meal, oats, and beans, are nitrogenous compounds, flesh-mak- 

 ing equivalents, yet they furnish only one part in a thousand 

 of the article we need, — phosphorus, — while cut straw, pota- 

 toes and several other " inferior " vegetables contain more than 

 double the quantity of the same. So that an animal must eat 

 such rubbish as straw, potatoes, carrots, beets, and "stubble" in 

 order to supply the necessary material. 



Then consider that sulphur, iron, chlorine, lime, potassium, 

 magnesium, and several other mineral substances, not in the 

 least nutritious, are alike necessary for the support and integrity 

 of the living organism, and therefore, should be the elements 

 of food. Some articles furnish the needful in abundance, in 

 others there is a deficiency. This furnishes another argument 

 in favor of variations in diet. 



A lecturer on physiology has remarked, that " there exists 



