154 



LIFE. 



stances slightly heated, produce the union of 

 oxygen and hydrogen in an explosive mixture. 

 The action of sulphuric acid on alcohol in pro- 

 ducing ether, without itself undergoing change, 

 appears referable to the same class along with 

 those just described. We may consider it 

 proved, then, that many substances possess 

 the power of exercising upon compound bodies 

 an influence essentially distinct from what is 

 known as chemical affinity an influence which 

 consists in the production of a displacement 

 and new arrangement of their elements, without 

 themselves directly participating in it. Assu- 

 redly such a power, which is capable of effect- 

 ing chemical reactions in inorganic substances 

 as well as in organised bodies, though still too 

 little known to be accurately explained, must 

 play a far more important part throughout na- 

 ture than we have hitherto been led to suppose. 

 " In defining it a new power," says Berzelius 

 with philosophic caution, " I am far from 

 wishing to deny that some connexion exists 

 between its influences and the electro-chemical 

 ones with which we are familiar. On the con- 

 trary, I am very much disposed to recognize 

 it as a peculiar manifestation of these same 

 influences."* 



Another interesting series of facts, which 

 seem to confirm the theory of the operation 

 of chemical affinity in the living body, is that 

 which relates to the evolution of electricity 

 during the ordinary processes of growth both 

 in plants and animals. The late researches of 

 Dr. Faraday have fully proved the identity of 

 electrical attraction with chemical affinity, and 

 have shown that all chemical changes are at- 

 tended with a disturbance of electric equili- 

 brium. If, therefore, the changes occasioned 

 by the growth of organised systems are imme- 

 diately governed by laws similar to those which 

 preside over inorganic matter, we should ex- 

 pect to find that electricity is constantly being 

 developed by them in the same manner as we 

 obtain it by chemical decomposition or recom- 

 position. There is no deficiency of evidence that 

 such is the case, as the results of late inquiries 

 most abundantly testify .f 



That chemists have not been more successful 

 in imitating the operations of vital chemistry, 

 by the artificial production of organic com- 

 pounds, is due not only to their ignorance of 

 the composition of such bodies, but to their 

 want of acquaintance with the form or con- 

 dition in which they must be brought together, 

 in order to enter into the desired union. F^very 

 one conversant with chemical operations is well 

 aware of the important influence thus exerted. 

 A slight change of temperature, for example, 

 often reverses the affinities of a body: and many 

 elements are susceptible of particular actions 

 when in a nascent state (i. e. when in the act 



* This eminent chemist has been quoted as an 

 advocate of the doctrine of vital affinities. If such 

 was formerly held by him, it is evident, from the 

 tenor of the communication here referred to, that 

 he has abandoned it. 



t See the Author's essay on the laws regulating 

 vital and physical phenomena, in Edinb. PJiilos. 

 Journal for Apiil 1838; and Principles of General 

 and Comparative Physiology, p. 379 et seq. 



of being freed from some other combination) 

 which in their ordinary condition could not be 

 so affected. When it is considered, therefore, 

 how little we know of the operation of such 

 conditions in the laboratory of life, no surprise 

 will be felt that its results should often appear 

 contrary to what might have been anticipated. 

 No reasonable ground has yet been adduced 

 for supposing that, if we had the power of 

 bringing together the elements of any organic 

 compound in their requisite states and propor- 

 tions, the result would be any other than that 

 which it is found to be in the living body; for 

 the agency of vitality, as Dr. Prout justly re- 

 marks, " does not change the properties of the 

 elements, but simply combines them in modes 

 which we cannot imitate." 



It is hoped that the foregoing statements will 

 have established the probability (which is all 

 that the present state of our knowledge on 

 these subjects will allow us to assert) that the 

 affinities which hold together the elements of 

 living bodies, and which govern the elaboration 

 of organic products, are the same as those con- 

 stantly operating in the world around. It 

 would seem, at any rate, premature to assert 

 that the operations of vital chemistry are di- 

 rected by distinct laws and due to new forces. 

 The designations organic and vital affinity 

 seem to have been employed by some writers 

 to express only the peculiarities of the circum- 

 stances and conditions under which these laws 

 usually operate, rather than any real difference 

 in the nature of the powers thettiselves. And 

 others appear to use them as provisional terms 

 only, referring those effects to the operation of 

 vitality which chemistry is not yet in a condi- 

 tion to explain. In the former sense it is ma- 

 nifest that such employment of the term is in- 

 jurious as leading to misconception. In the 

 latter it is harmless, if it do not check inquiry 

 and create a prejudice against the reception of 

 new facts. The period when all difficulty shall 

 have vanished from the application of chemical 

 laws to the phenomena of the vital economy 

 may be very far distant ; and in the mean time 

 " we must be content with gathering a few in- 

 dications which occasionally break out from the 

 clouds of mystery in which the subject is ob- 

 scured." But it must not be left out of view 

 that every fresh discovery adds to the number 

 of these indications, and that they all point in 

 the same direction ; so that the probability of 

 the universal operation of chemical affinity in 

 the living body becomes every day more strong, 

 and the difficulty in proving the existence of a 

 distinct set of vital affinities is constantly be- 

 coming less easily surmounted. 



VI. VITALITY IN A DORMANT OR INACTIVE 

 CONDITION. There are many organised beings 

 at particular periods of whose existence all 

 vital action seems to be suspended ; and this 

 may result either from the absence of the sti- 

 muli necessary to maintain it, or from some 

 change in the organism itself, by which it be- 

 comes for a time less capable of responding to 

 these stimuli. When vital action is suspended 

 from the deficiency of external stimuli, one of 

 two things must happen ; either the vitality of 

 the organism will be destroyed by the disin- 



