152 



LIFE. 



as a simple body, like chlorine, iodine, or cya- 

 nogen, with the metal sodium.* 



It will be seen, then, that the tendency of 

 modern researches in inorganic chemistry is to 

 prove, that the mode of combination which 

 characterises the union of its elements, is not 

 by any means so simple as it has been usually 

 supposed; but that a binary, a ternary, and 

 perhaps even a quaternary compound, may 

 perform the part of an element, combining 

 with other elements which are really simple, to 

 form what are regarded as simple binary com- 

 pounds. We shall now enquire what reason 

 there is for believing that the compounds with 

 which organic chemistry supplies us, have a 

 similar constitution. VVe must be content, 

 however, with selecting one or two examples 

 from among the vast number which the in- 

 dustry of analytic chemists is constantly bring- 

 ing to light. The vegetable alkaloids have been 

 generally regarded as proximate principles, not 

 to be separated into simple compounds without 

 an entire disunion of their elements. They all 

 contain one equivalent of nitrogen ; and there 

 is good reason to suspect that this element is 

 not equally combined with all the rest, but 

 exists in union with hydrogen in the form of 

 ammonia, to which the alkaline power of these 

 substances is due. Again, camphor was long 

 considered a proximate principle of ternary 

 composition ; but it is now found to be an 

 oxide of camphene, a compound radical con- 

 sisting of carbon and hydrogen, which will 

 unite, like cyanogen, with simple bodies ; form- 

 ing camphoric acid with another equivalent of 

 oxygen, and entering with chlorine, &c. into 

 other compounds. Lastly, urea may be men- 

 tioned, in which the four elements that com- 

 pose it may be regarded as existing in several 

 forms of binary combination. It contains these 

 elements in the following proportions : 2 oxy- 

 gen, 4 hydrogen, 2 carbon, and 2 nitrogen. 

 These may be considered as existing in the 

 form of cyanic acid, ammonia, and water; one 

 equivalent of each of these forming cyanate of 

 ammonia; and, in fact, by the artificial union 

 of these compounds, urea has actually been 

 produced. It is by no means certain, however, 

 that these compounds exist as such in urea ; 

 and various ideas of its composition are enter- 

 tained by chemists, on which this is not the 

 place to comment. Our object is simply to 

 show the analogy in the composition of the 

 products of vital chemistry with that of the ar- 

 tificial compounds whose formation is subject 

 to none but physical laws. Why the chemist 

 is not more successful in imitating in his labo- 

 ratory the operations of the living economy, 

 will presently become subject for consideration. 

 An argument employed by many physiolo- 

 gists for the existence of a distinct set of vital 

 affinities, is founded upon the evident truth, 

 that the tissues and fluids which maintain a 

 certain composition when possessed of vitality, 

 speedily resolve themselves into new combina- 

 tions when this has become extinct. Hence it 

 is inferred that the affinities which hold toge- 



" See Graham's Chemistry, p. 158 et scq. 



ther the elements during life, are of a different 

 nature from those which operate in producing 

 their subsequent separation. Now, it may be 

 objected to this inference, that no solid or fluid 

 compounds which have a disposition to spon- 

 taneous decay after death, can continue to exist 

 without change during life ; that the activity of 

 the processes of interstitial absorption and re- 

 position seems to bear a pretty constant ratio, 

 in every case, with the natural tendency to de- 

 composition ; and that the maintenance of the 

 original combination is not so much owing to 

 anything peculiar in the affinities which hold 

 together its elements, as to the constant removal 

 of particles in a state of incipient decay, and 

 their replacement by others freshly united. 

 Thus, we find that all the most permanent parts 

 of the animal frame, such as the massive skele- 

 tons of the polypifera, the calcareous tegument 

 of the mollusca, or the bony scales of fishes, 

 to the possible duration of which geologists 

 scarcely dare to assign a limit, are extravascular 

 in the living animal, undergoing scarcely any 

 interstitial change when once formed. Next 

 to these in order of durability are the osseous 

 structures of animals, and the woody fibre of 

 plants, whose connection with the circulating 

 system appears rather adapted to meet the exi- 

 gencies of growth, injury, or disease, than to 

 maintain a constant change required by the ten- 

 dency to decomposition. When we examine 

 the softer tissues, on the other hand, we find 

 that the rapidity of interstitial change fully 

 compensates for the increased tendency to de- 

 cay; and that the perfect exercise of their 

 respective functions imperatively demands the 

 constant maintenance of their normal constitu- 

 tion. Moreover, there are many organic com- 

 pounds which are as permanent as those formed 

 in the laboratory of the chemist ; of this kind 

 are gum, sugar, and many other proximate prin- 

 ciples, which simply require for their preserva- 

 tion such external conditions as are necessary 

 to prevent the spontaneous decomposition of 

 many inorganic bodies. The degree in which 

 these are subject to ordinary chemical opera- 

 tions will be presently mentioned. It appears, 

 then, to be an inference better founded on fact 

 than that first mentioned, that the preservation 

 of the normal constitution of organic com- 

 pounds in the living body, is dependent on the 

 continuance of the vital actions of the eco- 

 nomy, rather than due to its mere possession of 

 the property of vitality. In fact, that may be 

 reasonably maintained as an inference from 

 these phenomena, which we have already at- 

 tempted to prove on other grounds; that the 

 vitality of each tissue, that is to say, its posses- 

 sion of vital properties, is dependent on the 

 perfect condition of its organisation, and that, 

 so far from preserving the organism from decay, 

 it merely remains until decay has commenced. 

 These inferences are, we think, fully borne out 

 by the two following facts. When life is being 

 extinguished by starvation, the whole body ex- 

 hales a putrid odour even before the occurrence 

 of death, and rapidly passes into putrefaction 

 afterwards : here it would seem that the process 

 of spontaneous decomposition, which we have 



