34 O'peration of A'^itrogen on Plants and Animals. [Jan., 



In regard to its relations to agriculture, the communication of 

 the Dr. manifests a research and attainment of physical science, 

 far ahead of the times in which he wrote; it is true he used 

 terms, septon, and septic acid, perhaps not now admissable, but 

 they conveyed clearly his comprehensive views upon an intricate 

 subject, and he directed the true course for way-worn travelers, 

 in a region of much obscurity; and for which others have unfair- 

 ly borne the palm. 



The principle, which he prescribed as a guide to the cultivator 

 of the soil, " that manures should contain what the plant is known 

 shall, upon analysis possess," is now well established, was, I 

 think, chiefly his own: his designation of septon (nitrogen,) as 

 an essential principle in manures, " for the tilling of the ear of 

 wheat," and the cerealia in general, if not original, was forcibly 

 illustrated and impressed by him, and he adds what a subsequent 

 experience has taught, " that without it the straw may be large 

 and heavy, but the grain will be scanty and light, yet in this 

 ground, he continues "turnips and others, that do not require sep- 

 ton, (nitrogen,) may thrive exceedingly." 



His introduction and connexion, as an auxiliary of practical 

 agriculture from vital principles of hygeine, in the use and appli- 

 cation of manures, and the forcible manner with which he im- 

 presses it, offer to the farmer a strong inducement to do his duty, 

 by removing the dead carcasses, and other such nuisances, from 

 the vicinity of his dwelling to his fields, for the two-fold purpose 

 of preserving his health, and contributing to his wealth and com- 

 fort. 



The deductions, which the author has drawn in this part of his 

 subject, from his facts, in then selves remarkable, in those facts of 

 comparative obscurity, of the chemical and physiological balance 

 of nature, in the animal and vegetable creation; and now, so well 

 established, and recently so well illustrated by Dumas and Bous- 

 singault, bespeak a philosophic acumen of no ordinary grade; 

 the one, the vegetable, a simple laboratory of natui-e, deriving the 

 elements for its operation, from the air and the earth, replete with 

 poisons to the animal class, purifying, digesting, and adapting 

 them for transformation, into the more complex nature, and fasti- 

 dious taste of the latter, which decomposes, appropriates, and 

 again vitiates them, to be again elaborated and refitted for his 

 future uses. How clearly and substantially has Dr. Mitchell, 

 half a century ago, discerned this obscure and salutary bond of 

 physical science, when he says, "noxious effluvia are repressed, 

 and their virulence counteracted by the mediation of plants;^' and 

 he adds, " the instrumentality of these two classes, (of organic 

 beings,) seem to be intended to keep the great balance of nature 

 in equijmse, and prevent either being overloaded "with materials 

 destructive to animal life." 



