18 



ANIMAL CHEMISTRY. 



ton of producing these substances; when 

 they have lost the power of transforming 

 the food into that shape in which it may, 

 by entering into combination with the oxy- 

 gen ol the air, protect the system from its 

 influence, then, the substance of the organs 

 themselves, the fat of the body, the sub- 

 stance of the muscles, the nerves, and the 

 brain, are unavoidably consumed.* 



The true cause of death in these cases is 

 the respiratory process, that is, the action of 

 the atmosphere. 



A deficiency of food, and the want of 

 power to convert the food into a part of the 

 organism, are both, equally a want of resist- 

 ance ; and this is the negative cause of the 

 cessation of the vital process. The flame 

 is extinguished, because the oil is consumed ; 

 and it is the oxygen of the air which has 

 consumed it. 



In many diseases substances are produced 

 which are incapable of assimilation. By 

 the mere deprivation of food, these sub- 

 stances are removed from the body without 

 leaving a trace behind ; their elements have 

 entered into combination with the oxygen 

 of the air. 



From the first moment that the function 

 of the lungs or of the skin is interrupted or 

 disturbed, compounds, rich in carbon, ap- 

 pear in the urine, which acquires a brown 

 colour. Over the whole surface of the body 

 oxygen is absorbed, and combines with all 

 the substances which offer no resistance to 

 it. In those parts of the body where the 

 access of oxygen is impeded ; for example, 

 in the armpits, or in the soles of the feet, 

 peculiar compounds are given out, recog- 

 nisable by their appearance, or by their 

 odour. These compounds contain much 

 carbon. 



Respiration is the falling weight, the bent 

 spring, which keeps the clock in motion ; 

 the inspirations and expirations are the 

 strokes of the pendulum which regulate it. 

 In our ordinary timepieces, we know with 

 mathematical accuracy the effect produced 

 0*1 their rate of going, by changes in the 

 length of the pendulum, or in the external 

 temperature. Few, however, have a clear 

 conception of the influence of air and tem- 

 perature on the health of the humaa body ; 

 and yet the research into the conditions ne- 

 cessary to keep it in the nominal state, is not 

 more difficult than in the case of a clock. 



V. The want of a just conception of force 

 and effect, and of the connection of natural 

 phenomena, has led chemists to attribute a 

 part of the heat generated in the animal 

 body to the action of the nervous system. 

 If this view exclude chemical action, or 

 changes in the arrangement of the elemen- 

 tary particles, as a condition of nervous 



* For an account of what really takes place in 

 this process, I refer to the considerations on the 

 means by which the change of matter is effected 

 in the body of the carnivora, which will be found 



agency, it means nothing else than to derive 

 the presence of motion, the manifestation of 

 a force, from nothing. But no force, no 

 power can come of nothing. 



No one will seriously deny the share 

 which the nervous apparatus has in the 

 respiratory process ; for no change of condi- 

 tion can occur in the body without the 

 nerves ; they are essential to all vital motions. 

 Under their influence, the viscera produce 

 those compounds, which, while they protect 

 the organism from the action of the oxygen 

 of the atmosphere, give rise to animal heat; 

 and when the nerves cease to perform their 

 functions, the whole process of the action 

 of oxygen must assume another form. 

 When the pons Varolii is cut through in the 

 dog, or when a stunning blow is inflicted on 

 the back of the head, the animal continues 

 to respire for some time, often more rapidly 

 than in the nominal state; the frequency 

 of the pulse at first rather increases than 

 diminishes, yet the animal cools as rapidly 

 as if sudden death had occurred. Exactly 

 similar observations have been made on the 

 cutting of the spinal chord, and of the par 

 vagum. The respiratory motions continue 

 for a time, but the oxygen does not meet 

 with those substances with which, in the 

 normal state, it would have combined ; be- 

 cause the paralysed viscera will no longer 

 furnish them. The singular idea that the 

 nerves produce animal heat, has obviously 

 arisen from the notion that the inspired oxy- 

 gen combines with carbon, in the blood 

 itself; in which case the temperature of the 

 body, in the above experiments, certainly, 

 ought not to have sunk. But, as we shall 

 afterwards see, there cannot be a more erro 

 neous conception than this. 



As by the division of the pneumogastric 

 nerves the motion of the stomach and the 

 secretion of the gastric juice are arrested, 

 and an immediate check is thus given to the 

 process of digestion, so the paralysis of the 

 organs of vital motion in the abdominal vis- 

 cera affects the process of respiration. These 

 processes are most intimately connected , 

 and every disturbance of the nervous system 

 or of the nerves of digestion re-acts visibly 

 on the process of respiration. 



The observation has been made, that heat 

 is produced by the contraction of the mus- 

 cles, just as in a piece of caoutchouc, which, 

 when rapidly drawn out, forcibly contracts 

 again, with disengagement of heat. Some 

 have gone so far as to ascribe a part of the 

 animal heat to the mechanical motions of 

 the body, as if these motions could exist 

 without an expenditure of force consumed 

 in producing them ; how then, we may asu:, 

 is this force produced ? 



By the combustion of carbon, by the solu- 

 tion of a metal in an acid, by the combina- 

 tion of the two electricities, positive and 

 negative, by the absorption of light, and even 

 by the rubbing of two solid bodies together 

 with a certain degres ; rapidity, heat may 

 be produced. 



