ANIMAL CHEMISTRY. 



The chemical force which kept the ele- 

 ments together acted as a resistance/ which 

 was overcome by the active vital force. 



Had both forces been equal, no kind of 

 sensible effect would have ensued. Had the 

 chemical force been the stronger, the living 

 part would have undergone a change. 



If we now suppose that a certain amount 

 of vita] force must have been expended in 

 bringing to an equilibrium the chemical 

 force, there must still remain an excess of 

 force, by which the decomposition was ef- 

 fected. This excess constitutes the mo- 

 mentum of force in the living part, by 

 means of which the change was produced ; 

 by means of this excess the part acquires a 

 permanent power of causing further decom- 

 positions, and of retaining its condition, 

 form, and structure, in opposition to exter- 

 nal agencies. 



We may imagine this excess to be re- 

 moved, and employed in some other form. 

 This would not of itself endanger the exist- 

 ence of the living part, because the opposing 

 forces would be left in equilibrio ; but, by 

 the removal of the excess of force, the part 

 would lose its capacity of growth, its power 

 to cause further decompositions, and its 

 ability to resist external causes of change. 

 If, in this state of equilibrium, oxygen (a 

 chemical agent) should be brought in con- 

 tact with it, then there would be no resist- 

 ance to the tendency of the oxygen to com- 

 b.ae with some element of the living part, 

 because its power of resistance has been 

 taken away by some other application of its 

 excess of vital force. According to the 

 amount of oxygen brought to it, a certain 

 proportion of the living part would lose its 

 condition of vitality, and take the form of a 

 chemical combination, having a composi- 

 tion different from that of the living tissue. 

 In a word, there would occur a change in 

 the properties of the living compound, or 

 what we have called a change of matter. 



If we reflect that the capacity of growth 

 or increase of mass in plants is almost un- 

 limited ; that a hundred twigs from a willow 

 tree, if placed in the soil, become a hundred 

 jrees ; we can hardly entertain a doubt, that 

 with the combination of the elements of the 

 food of the plant so as to form a part of it, 

 a fresh momentum of force is added in the 

 newly formed part to the previously existing 

 momentum in the plant; insomuch, that 

 with the increase of mass, the sum of vital 

 force is augmented. 



According to the amount of available vital 

 force, the products formed by its activity 

 from the food are varied. The composition 



and simple pulley, 30 Ibs. to the height of 100 

 feet, pass over a space of 100 feet, while his mus- 

 cular energy furnishes the equilibrium to a pres- 

 sure of 30 Ibs. Were the force which the man 

 could exert not greater than would suffice to keep 

 in equilibrium a pressure of 30 Ibs., he would be 

 unable to raise the weight to the height men- 

 tioned. 



1 of the buds, of the radical fibres, of the leaf, 

 of the flower, and of the fruit, are very dif- 

 | ferent one from the other ; and the chemical 

 force by which their elements are held toge- 

 ther is very different in each of these cases. 



Of the non-azotized constituents of plants 

 we may assert, that no part of the momen- 

 tum of force is expended in maintaining 

 their form and structure, when their ele- 

 ments have once combined in that order in 

 which they become parts of organs endued 

 with vitality. 



Very different is the character of the azo- 

 tized vegetable principles; for, when sepa- 

 rated from the plant, they pass, as is com- 

 monly said, spontaneously, into fermentation 

 and putrefaction. The cause of this de- 

 composition or transformation of their ele- 

 ments is the chemical action which the 

 oxygen of the atmosphere exercises on one 

 of their constituents. Now we know, that 

 as long as the plant exhibits the phenomena 

 of life, oxygen gas is given off from its sur- 

 face ; that this oxygen is altogether without 

 action on the constituents of the living plant, 

 for which, in other circumstances, it has the 

 strongest attraction. It is obvious, there- 

 fore, that a certain amount of vital force 

 must be expended, partly to retain the de- 

 ments of the complex azotized principles in 

 the form, order, and structure which belong 

 to them ; and partly as a means of resistance 

 against the incessant tendency of the oxygen 

 of the atmosphere to act on their elements, 

 as well as against that of the oxygen se- 

 parated in the organism of the plant b'y the 

 vital process. 



With the increase of these easily altered 

 compounds, in the flower and in the fruit, 

 for example, the sum of chemical force (the 

 free manifestation of which, counteracted by 

 an equal measure of vital force, is employed 

 to furnish resistance) also increases. 



The plant increases in mass until the vital 

 force inherent in it comes into equilibrium 

 with all the other causes opposed to its 

 manifestation. From this period, every new 

 cause of disturbance, added to those pre- 

 viously existing (a change of .temperature, 

 for example,) deprives it of the power of of- 

 fering resistance, and it dies down. 



In perennial plants (in trees, for example,) 

 the mass of the easily decomposable (azo- 

 tized) compounds, compared with that of 

 the non-azotized, is so small, that of the 

 whole sum of force, only a minimum is 

 expended as resistance. In animals, this 

 proportion is reversed. 



During every period of the life of a plant, 

 the available vital force (that which is not 

 neutralized by resistance) is expended only 

 in one form of vital manifestation, that of 

 growth or increase of mass, or the over- 

 coming of resistance. No part of this force 

 is applied to other purposes. 



In the animal organism, the vital force 

 exhibits itself, as in the plant, in the form 

 of the capacity of growth, and as the means 

 of resistance to external agencies ; but both 



