THE FARMER'S MAGAZINE. 



'179 



to differ in cold or hot climates. Nitrogen may be 

 derived by the plants from the atmosphere, as well 

 as from the soil and the manure ; and, till that 

 point be decided, the nitrof^enous theory rests un- 

 confirmed. 



Potatoes are stated to contain more than double 

 the quantity of flesh-forming and heating prin- 

 ciples that are found in turnips ; yet turnips are 

 well known to fatten cattle much better than pota- 

 toes, except when boiled or steamed for swine. 

 Cabbages and beetroot are stated to be equal, if 

 not superior to turnips; yet practice finds those 

 articles to be inferior for fattening. Carrots and 

 parsnips are stated to be very much superior to 

 turnips, the latter article almost sevenfold, being 

 nearly equal in the elements of forming llesh, and 

 of giving heat ; yet practice finds the very reverse, 

 and prefers the turnips in the largest utility. If 

 the amount of percentage fixes the value of any 

 article as food, then a high place must be given to 

 water in the 90 per cent, found in turnips and po- 

 tatoes : it being hard to conceive that this large 

 quantity does not operate a most important part in the 

 construction of organisms. And the presence of this 

 element is universal in a greater or less amount and 

 proportion. Water may be regarded as the matrix 

 or mould in which the other articles are compound- 

 ed to exert the joint purposes of action. 



In all cases now mentioned, it is not the presence 

 or quantity of the elements that confer their value, 

 but the mode, way, or manner, in whicli the prin- 

 ciples are combined among themselves, and with 

 other matters. The just and reasonable inference 

 seems to be, that a share of mixed nutrition is af- 

 forded by the various elements found in organized 

 bodies, nitrogenous, heat-making, and inorganic ; 

 and that no single result is effected by separate 

 elements, but by a joint contribution of the united 

 principles, in which all differences are annulled, 

 and one similar result obtained. Whatever char- 

 acter the substances may have outside the organ- 

 ism, they must quit them shortly after their entrance 

 into it, putting off specific differences, and merg- 

 ing all varieties in a vital unity. This deduction 

 is not exposed to the falsifications from practice, 

 and withstands all examinations. 



The same fallacy is found in the chemical re- 

 ports on the value of the grass plants. For 

 instance, several plants are stated to be very much 

 superior to the common ray grass in chemical con- 

 stituents of nutritive value ; but whatever that va- 

 lue may be, practice is satisfied that no grass plant, 

 yet known, is so valuable for the purposes of the 

 farmer, in growing readily on the greatest variety 

 of soils, in yielding a good bulk of produce in a 

 number of stems of medium height in the manner 

 of a grain crop, and a quantity of i;0und healthy 



seed that is easily gathered and conveniently manu- 

 factured. Chemistry made a most miserable failure 

 in the attempt to fix the character of grasses : the 

 ray grass is established on the grounds of true 

 science, on the science of agriculture itself, which 

 is the systematic experience of it. On this foun- 

 dation the structure of comparisons and results 

 must be built. 



Whatever the future progress of chemistry may 

 effect in the way of simplifying physiological prob- 

 lems — and none may doubt very large assistance 

 from its co-operation — there is one radical distinc- 

 tion, which will continue to keep the two sciences 

 separate. Chemical laws are quantitative be- 

 cause chemical actions are definite combinations ; 

 whereas physiological laws can never become quan- 

 titative, but only qualitative, because vital sub- 

 stances are indefinite, in composition ; while 

 chemical substances are formed by unvarying com- 

 binations of quantity, in so much acid to so much 

 base always forming the same salt; in so many 

 atoms of one substance always uniting with so 

 many of another to form a third. The substances 

 on which vital actions specially depend are never 

 precisely and accurately definite ; they vary in dif- 

 ferent organisms, and at different ages of the same 

 constitution ; and as every variation in composition 

 necessarily affects the property of each substance, 

 it is impossible that such actions can be reduced 

 to those exact quantitative formulae, on which 

 chemistry is founded. A salt is the same from the 

 sea, the plant, or manufactured in the laboratory; 

 but nerve tissue is never precisely the same; blood 

 and milk differ from similar sources; constitution 

 and temperament vary very considerably within cer- 

 tain limits, but widely enough to overthrow any 

 correct inferences or settled deductions, as in cases 

 of definite and permanent constitutions. 



The chemical mode of fixing the exhausting 

 powers of green crops from the ashes of straw and 

 grain, is equally fallacious with the quality of food. 

 The ashes of grain and straw exhibit a composition 

 of silica, in the largest quantity, earthy phosphates, 

 and carbonates, soluble salts, potash, and a small 

 ratio of metallic oxides. These matters are sup- 

 posed to be drawn from the soil, which is impover. 

 ished by the loss ; and the restoration is made by 

 the application of manure. This scientific mode 

 of fixing the exhausting powers of plants is exposed 

 to uncertainty, if plants extract from the soil, and 

 transmit, as part of the composition, the matters 

 that are found both in the soil and in the plants j 

 or, if the substances are not formed by the process 

 of vegetation, from matters wholly different. It is 

 certain that substances are found in the soil, which 

 do not appear in the plants ; and that the plants 

 contain matters, of which no vestige can be found 



