ORGANIC SUBSTANCES. 



misting between the elements of a body gives 

 rise to a transformation. The elements ar- 

 range themselves according to the degrees 

 of their reciprocal attraction into new com- 

 binations, which are incapable of farther 

 change under the same conditions. 



The products of these transformations 

 vary with their causes, that is, with the dif- 

 ferent conditions on which their production 

 depended ; and are as innumerable as these 

 conditions themselves. The chemical cha- 

 racter of an acid, for example, is its un- 

 ceasing disposition to saturation by means 

 of a base ; this disposition differs in intensity 

 i different acids ; but when it is satisfied, 

 the acid character entirely disappears. The 

 chemical character of a base is exactly the 

 reverse of this, but both an acid and a base, 

 notwithstanding the great difference in their 

 properties, effect, in most cases, the same 

 kinl of transformations. 



Hvdrocyanic acid and water contain the 

 elements of carbonic acid, ammonia, urea, 

 cyanuric acid, cyanilic acid, oxalic acid, for- 

 mic acid, melam, ammelin, melamin, azulmin, 

 mdlon, hydromellonic acid, allantoin, fyc. It 

 is well known, that all these very different 

 substances can be obtained from hydrocyanic 

 acid and the elements of water, by various 

 chemical transformations. 



The whole process of nutrition may be 

 understood by the consideration of one of 

 these transformations. 



Hydrocyanic acid and water, for example, 

 when brought into contact with muriatic 

 acid, are decomposed into formic acid and 

 ammonia ; both of these products of decom- 

 position contain the elements of hydrocyanic 

 acid and water, although in another form, 

 and arranged in a different order. The 

 change results from the strong disposition 

 or struggle of muriatic acid to undergo satu- 

 ration, in consequence of which the hydro- 

 cyanic acid and water suffer mutual decom- 

 position. The nitrogen of the hydrocyanic 

 acid and the hydrogen of the water unite 

 together and form a base, ammonia, with 

 which the acid unites ; the chemical charac- 

 ters of the acid being at the same time lost, 

 because its desire for saturation is satisfied 

 by its uniting with ammonia. Ammonia 

 itself was not previously present, but only 

 its elements, and the power to form it. The 

 simultaneous decomposition of hydrocyanic 

 acid and water in this instance does not take 

 place in consequence of the chemical affinity 

 of muriatic acid for ammonia, since hydro- 

 cyanic acid and water contain no ammonia. 

 An affinity of one body for a second which 

 is totally without the sphere of its attrac- 

 tions, or which, so far as it is concerned, 

 does not exist, is quite inconceivable. The 

 ammonia in this case is formed only on ac- 

 count of the existing attractive desire of the 

 acid for saturation. Hence we may perceive 

 how much these modes of decomposition, to 

 which the name of transformations or meta- 

 morphoses has been especially applied, differ 

 from the ordinary chemical (iecompositions. 

 4 



In consequence of the formation of am- 

 monia, the other elements of hydrocyanic 

 acid, namely, carbon and hydrogen, unite 

 with the oxygen of the decomposed water, 

 and form formic acid, the elements of this 

 substance with the power of combination 

 being present. Formic acid here represents 

 the excremenlitious matters ; ammonia, the 

 new substance, assimilated by an organ of a 

 plant or animal. 



Each organ extracts from the food pre- 

 sented to it what it requires for its own sus- 

 tenance; while the remaining elements, 

 which are not assimilated, combine together 

 and are separated as excrement. The ex- 

 crementitious matters of one organ come in 

 contact with another during their passage 

 through the organism, and in consequence 

 suffer new transformations ; the useless mat- 

 ters rejected by one organ containing the 

 elements for the nutrition of a second and a 

 third organ : but at last, being capable of no 

 farther transformations, they are separated 

 from the system by the organs destined for 

 that purpose. Each part of an organized 

 being is fitted for its peculiar functions. A 

 cubic inch of sulphuretted hydrogen intro- 

 duced into the lungs would cause instant 

 death, but it is formed, under a variety of 

 circumstances, in the intestinal canal with- 

 out any injurious effect. 



In consequence of such transformations 

 as we have described, excrements are formed 

 of various composition, some of these con- 

 tain carbon in excess, others nitrogen, and 

 others again hydrogen and oxygen. The 

 kidneys, liver, and lungs, are organs of ex- 

 cretion ; the first separate from the body all 

 those substances in which a large propor- 

 tion of nitrogen is contained; the second, 

 those with an excess of carbon ; and the 

 third, such as are composed principally of 

 oxygen and hydrogen. Alcohol, also, and 

 the volatile oils which are incapable of be- 

 ing assimilated, are exhaled through the 

 lungs, and not through the skin. 



Respiration must be regarded as a slow 

 process of combustion or constant decompo- 

 sition. If it be subject to the laws which 

 regulate the processes of decomposition gene- 

 rally, the oxygen of the inspired air cannot 

 combine directly with the carbon of com- 

 pounds of that element contained in the 

 blood; the hydrogen only can combine with 

 the oxygen of the air, or undergo a higher 

 degree of oxidation. Oxygen is absorbed 

 without uniting with carbon ; and carbonic 

 acid is disengaged, the carbon and oxygen 

 of which must be derived from matters pre- 

 viously existing in the blood.* 



* The examination of the air expired by con- 

 sumptive persons, as well as of their blood, would 

 doubtless throw much light on the nature of phthisis 

 pulmonaris. Considered in a chemical point of 

 view, the decomposition of the blood, as it takes 

 place in the lungs, is a true process of putrefac- 

 tion. (See Part II.) The lungs are also the seat 

 of the transformation of the various substances 

 contained in the blood. It certainly well merit* 



