mixed with an alkaline solution, as of soda or potash. The alkali displaces 

 glycerine and combines with the acid. Soaps, therefore, are oleates, 

 palmitates, margarates, or stearates of soda, or potash, or lime. These salts, 

 as they may be called, are capable of traversing animal membranes, which 

 is not readily accomplished by the oils in their natural state. 



The volatile oils are very numerous, and give to different plants their 

 peculiar and characteristic odours. Thus the smell of new-mown hay is 

 due to the volatile oil (cumarin) which is contained in the Anihoxanthum 

 odoratum, the odour of mint to the oil of mint, and so on; the quantity 

 being usually small, in mint, for example, not exceeding 1 or 2 per cent of 

 the dried plant. 



In regard to the salts, they may be divided into two groups — those 

 formed by the so-called mineral acids, such as the sulphuric, nitric, phos- 

 phoric, hydrochloric, and silicic acids, in combination with the bases, 

 sodium, potassium, magnesium, lime, and others; and those formed by the 

 organic acids, which are combined with the same bases, and of which the 

 chief are oxalic acid, found in such plants as the oxalis, dock, rhubarb, and 

 spinach, malic acid in apples, tartaric acid in the grape, formic acid in the 

 nettle, acetic acid in chamomile, propionic acid in milfoil, butyric acid in the 

 pansy, and many others. 



If we now consider the composition of the ordinary food of the horse 

 in the light of these preliminary remarks, we shall find that whilst such 

 substances as oats and maize can be analysed with great exactness, it is 

 almost impossible to give even an approximate account of the composition 

 of hay, since it varies with the soil, the species forming the herbage, and 

 even with the period of growth of the plants of which it is composed; 

 the saccharine principles being most abundant at the period of inflor- 

 escence, mucilage during the period of the maturation of the seed, and 

 the proteids, saline and bitter substances in the aftermath or later crop. 

 The analyses of M. Boussingault give as the average percentage compo- 

 sition of ordinary hay — Water, from 13 to 16 parts; proteids, 7 to 13 "5; 

 sugars and starch, 44; woody tissue and cellulose, 24; fats, 4; ashes, 5 to 8 

 parts. A large proportion of the ashes consists of silex, and the remainder 

 is nearly all composed of the salts of calcium, potassium, and sodium. The 

 composition of oats is — Water, 12; proteids, 10 to 14; fats, 5 to 7 ; starches, 

 gum, and sugar, 50 to 55; woody fibre, 10; and salts, 3. Of maize — "Water. 

 13; proteids, 10 to 15; fat, 4 - 5; farinaceous compounds, 68"5; woody fibre, 

 2 "5; ashes, 1*5. It may just be added that the proportion of nitrogen to 

 carbohydrate in the different cereals is as follows: — wheat, 2 '29 : 78 "64; rye, 

 2-17:78-81; barley, 2-06:75"29; oats, 1-90:65-93; maize, 1-81:78-74; 

 rice, T45 : 88 - 01; millet, T95 : 76 - 09. In green food the quantity of water 



