ANIMAL CHEMISTRY. 



cona w^e 30 Ibs. to a height of 200 feet ; then 

 the latter has expended twice as much force 

 as the former. A third who raises 60 Ibs. to 

 a height of 50 feet, expends no more force 

 than the iirst did in raising 30 Ibs. to the 

 height of 100 feet. The momentum of mo- 

 tion of the first (30x100) is equal to that 

 of the third (60x50) while that of the se- 

 cond (30x200) is twice as great. 



Momentum of force and momentum of 

 motion in mechanics are therefore expres- 

 sions or measures for effects of force, having 

 reference to the velocity attained in a given 

 time, or to a given space ; and in this sense 

 may be applied to the effects of all other 

 causes of motion, or of change in form and 

 structure, however great or however small 

 may be the space or the time in which their 

 effects are displayed to the senses. 



Every force, therefore, exhibits itself in 

 matter either in the form of resistance to 

 external causes of motion, or of change in 

 form and structure; or as a moving force 

 when no resistance is opposed to it; or, 

 finally, in overcoming resistance. 



One and the same force communicates 

 motion and destroys motion ; the former 

 when its manifestations are opposed by no 

 resistance ; the latter, when it puts a stop to 

 the manifestation of some other cause of 

 motion, or of change in form and structure. 

 Equilibrium or rest is that state of activity 

 in which one force or momentum of motion 

 is destroyed by an opposite force or momen- 

 tum of motion. 



We observe both these manifestations of 

 activity in that force which gives to the liv- 

 ing tissues their peculiar properties. 



The vital force appears as a moving force 

 or cause of motion when it overcomes the 

 chemical forces (cohesion and affinity) which 

 act between the constituents of food, and 

 when it changes the position or place in 

 which their elements occur; it is manifested 

 as a cause of motion in overcoming the che- 

 mical attraction of the constituents of food, 

 and is, further, the cause which compels 

 them to combine in a new arrangement, and 

 to assume new forms. 



It is plain that a part of the animal body 

 possessed of vitality, which has therefore the 

 power of overcoming resistance, and of giv- 

 ing motion to the elementary particles of the 

 food, by means of the vital force manifested 

 in itself must have a momentum of motion, 

 which is nothing else than the measure of 

 the resulting motion or change in form and 

 etructure. 



We know that this momentum of motion 

 in' the vital force, residing in a living part, 

 may be employed in giving motion to bodies 

 at rest, (that is, in causing decomposition, 

 or overcoming resistance,) and if the vital 

 force is analogous in its manifestations to 

 other forces, this momentum of motion must 

 be capable of being conveyed or communi- 

 cated by matters, which in themselves do 

 not destroy its effect by an opposite mani- 

 festation of force. 



Motion, by whatever cause produced, 

 cannot in itself be annihilated ; it may indeed 

 become inappreciable to the senses, buteveu 

 when arrested by resistance (by the mani- 

 festation of an opposite force,) its effect is 

 not annihilated. The falling stone, by means 

 of the amount of motion acquired in its de- 

 scent, produces an effect when it reaches 

 the table. The impression made on the 

 wood, the velocity communicated by its 

 parts to those of the wood, all this is its effect. 



If we transfer the conceptions of motion, 

 equilibrium, and resistance, to the chemical 

 forces, which, in their modus operandi, ap- 

 proach to the vital force infinitely nearer 

 than gravitation does, we know with the 

 utmost certainty, that they are active only 

 in the case of immediate contact. We know, 

 also, that the unequal capacity of chemical 

 compounds to offer resistance to external 

 disturbing influences, to those of heat, or of 

 electricity, which tend to separate their par- 

 ticles, as well as their power of overcoming 

 resistance in other compounds (of causing 

 decomposition); that, in a word, the active 

 force in a compound depends on a certain 

 order or arrangement, in which its element- 

 ary particles touch each other. 



The same elements, united in a different 

 order, when in contact with other com- 

 pounds, exert a most unequal power of of- 

 fering or overcoming resistance. In one 

 form the force manifested is available (the 

 body is active, an acid, for example) ; in 

 another not (the body is indifferent, neutral) ; 

 in a third form, the momentum of force is 

 opposed to that of the first (the body is 

 active, but a base). 



If we alter the arrangement of the ele- 

 ments, we are able to separate the constitu- 

 ents of a compound by means of another 

 active body ; while the same elements, united 

 in their original order, would have opposed 

 an invincible resistar. ce to the action of the 

 decomposing agent. 



In the same way as two equal .nelastic 

 masses, impelled with equal velocity from 

 opposite points, on coming into contact are 

 brought to rest ; in the same way, therefore, 

 as two equal and opposite momenta of mo- 

 tion mutually destroy each other; so may 

 the momentum of force in a chemical corn- 

 pound be destroyed in whole or in part by 

 an equal or unequal, and opposite momen- 

 tum of force in a second compound. But 

 it cannot be annihilated as long as the ar- 

 rangement of 'he elementary particles, by 

 which its inherent force was manifested, is 

 not changed. 



The chemical force of sulphuric acid is 

 present in sulphate of lime as entire as in 

 oil of vitriol. It is not appreciable by the 

 senses; but if the cause be removed which 

 prevented its manifestation, it appears in its 

 full force in the compound in which it pro- 

 perly resides. 



Thus the force of cohesion in a solid may 

 disappear, to the senses, from the action of" 

 a chemical force, (in solution,) or of heat 



