ANIMAL CHEMISTRY. 



thy of bil e secreted increases ; while that of 

 the fat present in the body diminishes in the 

 same proportion. 



For carrying on the involuntary motions 

 in the animal body, a certain amount of vital 

 force is expended at every moment of its 

 existence; and, consequently, an incessant 

 change of matter goes on; but the amount 

 of living tissue, which, in consequence of 

 this form of consumption of vital force, 

 loses its condition of life and its capacity of 



?rowth, is confined within narrow limits, 

 t is directly proportional to the force re- 

 quired for these involuntary motions. 



Now, although we may suppose that the 

 living muscular tissue, with a sufficient sup- 

 ply of food, never loses its capacity of 

 growth ; that this form of vital manifestation 

 is continually effective ; this cannot apply to 

 those parts of the body whose available vital 

 force has been expended in producing me- 

 chanical effects. For the waste of matter, 

 in consequence of motion and laborious 

 exertion, is extremely various in different 

 individuals. 



If we reflect, that the slightest motion of 

 a finger consumes force ; that in conse- 

 quence of the force expended, a correspond- 

 ing portion of muscle diminishes in volume; 

 it is obvims, that an equilibrium between 

 supply and waste of matter (in living tissues) 

 can only occur when the portion separated 

 or expelled in a lifeless form is, at the same 

 instant in which it loses its vital condition, 

 restored in another part. 



The capacity of growth or increase in 

 mass depends on the momentum of force 

 belonging to each part ; and must be capable 

 of continued manifestation (if there be a suf- 

 ficient supply of nourishment,) as long as it 

 does not lose this momentum, by expending 

 it, for example, in producing motion. 



In all circumstances, the growth itself is 

 restricted to the time : that is to say, it can- 

 not be unlimited in a limited time. 



A living part cannot increase in volume 

 at the same moment in which a portion of 

 it loses the vital condition, and is expelled 

 from the organ in the form of a lifeless com- 

 pound ; on the contrary, its volume must 

 diminish. 



The continued application of the momen- 

 tum of force in living tissues to mechanical 

 effects determines, therefore, a continued 

 separation of matter ; and only from the pe- 

 riod at which the cause of waste ceases to 

 operate, can the capacity of growth be ma- 

 nifested. 



Now, since, in different individuals, ac- 

 cording to the amount of force consumed in 

 producing voluntary mechanical effects, un- 

 equal quantities of living tissue are wasted, 

 there must occur, in every individual, unless 

 the phenomena of motion are to cease en- 

 tirely, a condition in which all voluntary 

 motions are completely checked, in which, 

 therefore, these occasion no waste. This 

 condition is called sleep. 



The growth of one part, which is not de- 



prived of its vital force, cannot be in the 

 slightest degree affected by the consumption 

 of the vital force of another part in producing 

 motion. The one may increase in volume, 

 while the other diminishes ; and the waste 

 in one can neither increase nor diminish the 

 supply in the other. 



Now, since the consumption of force for 

 the involuntary motions continues in sleep, 

 it is plain that a waste of matter also con- 

 tinues in that state ; and if the original equi- 

 librium is to be restored, we must suppose 

 that, during sleep, an amount of force is ac- 

 cumulated in the form of living tissue, 

 exactly equal to that which was consumed 

 in voluntary and involuntary motion during 

 the preceding waking period. 



If the equilibrium between waste and 

 supply of matter be in the least degree dis- 

 turbed, this is instantly seen in the different 

 amount of force available for mechanical 

 purposes. 



It is further obvious, that if there should 

 occur a disproportion between the conduct- 

 ing power of the nerves of voluntary and 

 involuntary motion, a difference in the phe- 

 nomena of motion themselves will be per- 

 ceptible, in the same proportion as the one 

 or the other is capable of propagating the 

 momentum of force, generated by the change 

 of matter. As the motions of the circulating 

 system and of the intestines increase, the 

 power of producing mechanical effects in 

 the limbs must diminish in the same propor- 

 tion (as in wasting fevers ;) and it, in a given 

 time, more vital force has been consumed 

 for mechanical purposes (labour, running, 

 dancing, &,c.,) than is properly available for 

 the voluntary and involuntary motions ; if 

 force be expended more rapidly thin the 

 change of matter can be effected in the same 

 time ; then a part of that force whi^h is 

 necessary for the involuntary motions must 

 be expended in restoring the excess of force 

 consumed in voluntary motion. The mo- 

 tions of the heart and of the intestines, in 

 this case,, will be retarded, or will entirely 

 cease. 



From the unequal degree of conducting 

 power in the nerves, we must deduce those 

 conditions which are termed paralysis, syn- 

 cope, and spasm. Paralysis of the nerves 

 of voluntary motion may exist without ema- 

 ciation ; but frequently recurring attacks of 

 epilepsy (in which vital force is rapidly 

 wasted in producing mechanical effects) are 

 always accompanied by remarkably rapid 

 emaciation. 



It ought to excite the highest admiration 

 when we consider with what infinite wis- 

 dom the Creator has divided the means by 

 which animals and plants are qualified for 

 their functions, for their peculiar vital mani- 

 festations. 



The living part of a plant requires the 

 whole force and direction of its vital energy 

 from the absence of all conductors of force. 

 By this means the leaf is enabled to over- 

 come the strongest chemical attractions, to 



