34 



ANIMAL CHEMISTRY. 



given off were contained, as such, in the 

 starch,, or not. 



If they were ready formed in the starch 

 the separation might occur without the dis- 

 engagement of heat ; but if the carbon and 

 hydrogen were present in any other form in 

 the starch, (or in the compound from which 

 the fat was produced,) it is obvious that a 

 change in the arrangement of the atoms 

 must have occurred, in consequence of which 

 the atoms of the carbon and of the hydrogen 

 have united with those of the oxygen, to 

 form carbonic acid and water. 



Now, so far as chemical researches have 

 gone, our knowledge of the constitution of 

 starch, and of the varieties of sugar, will justify 

 no other conclusion than this, that these sub- 

 stances contain no ready formed carbonic acid. 



We are acquainted with a large number 

 of processes of metamorphosis of a similar 

 kind, in which the elements of carbonic acid 

 and water are separated from certain pre- 

 existing compounds; and we know with 

 certainty that all these processes are accom- 

 panied by a disengagement of heat, exactly 

 as if the carbon and hydrogen combined 

 directly with oxygen. 



Such a disengagement of carbonic acid, 

 for example, occurs in all processes of fer- 

 mentation or putrefaction, which are, with- 

 out exception, accompanied with a genera- 

 tion of heat. 



In the fermentation of a saccharine solu- 

 tion, in consequence of a new arrangement 

 of the elements of the sugar, a certain part 

 of its carbon and oxygen unite to form car- 

 bonic acid, which separates as gas; and as 

 another result of this decomposition, we ob- 

 tain a volatile combustible liquid, containing 

 little oxygen, namely, alcohol. 



If we add to 2 equivalents of sugar the 

 elements of 12 equivalents of water, and 

 subtract from the sum of the atoms 24 equi- 

 valents of oxygen, there remain 6 equiva- 

 lents of alcohol. 



O 24 = C"H 36 O l *= 6 

 eq. alcohol. 



These 24 equivalents of oxygen suffice to 

 oxidize completely a third equivalent of 

 sugar that is, to convert its carbon into 

 carbonic acid and its hydrogen into water, 

 and by this oxidation we recover the 12 

 equivalents of water supposed to be added 

 in the former part of the process, exactly as 

 if this water had taken no share in it. 



C 12 H 12 O 12 +O 24 = ISCO 2 ^ 12HO. 



According to the ordinary view, 12 equi- 

 valents of carbonic acid separate from 3 of 

 sugar, yielding 6 of alcohol that is, exactly 

 the same amount of these products as if two- 

 thirds of the sugar had yielded oxygen to the 

 remaining third, so as completely to oxidize 

 'ts elements. 



C 36 H 36 O 36 =C 3 *H 86 O 12 + 12CO a * 



* For an explanation of the formulae and equa- 

 tions employed, see the Introduction to the Ap- 

 pendix. 



By a comparison of tl.ese two methods of 

 representing the same cnange, it will easily 

 b'e seen that the division or splitting of a 

 compound like sugar into carbonic acid, on 

 the one hand, and a compound containing a 

 little oxygen on the other, is in its results 

 perfectly equivalent to a separation of oxy- 

 gen from a certain portion of the compound, 

 and the oxidation or combustion of another 

 portion of it at the expense of this oxy- 

 gen. 



It is well known that the temperature of 

 a fermenting liquid rises ; and if we assurna 

 that a hogshead of wort, holding 1,200 litres 

 = 2,400 Ibs., French weight, contains 16 

 per cent, of sugar, in all 384 Ibs., then, dur- 

 ing the fermentation of this sugar, an amount 

 of heat must be generated equal to that 

 which would be produced by the combus- 

 tion of 51 Ibs. of carbon. 



This is equal to a quantity of heat by 

 which every pound of the liquid might be 

 heated by 297 - 9; that is, supposing the 

 decomposition of the sugar to occur in a 

 period of time too short to be measured. 

 This is well known not to be the case ; the 

 fermentation lasts five or six days, and each 

 pound of liquid receives the 207-9 degrees 

 of heat during a period of 120 hours. In 

 each hour there is, therefore, set free an 

 amount of heat capable of raising the tem- 

 perature of each pound of liquid 1-4 degree; 

 a rise of temperature which is very power- 

 fully counteracted by external cooling and 

 by the vaporization of alcohol and water. 



The formation of fat, like other analogous 

 phenomena in which oxygen is separated 

 in the form of carbonic acid, is consequently 

 accompanied by a disengagement of heat. 

 This change supplies to the animal body a 

 certain proportion of the oxygen indispens- 

 able to the vital processes; and this espe- 

 cially in those cases in which the oxygen 

 absorbed by the skin and lungs is not suf- 

 ficient to convert into carbonic acid the 

 whole of the carbon adapted for this com 

 bination. 



This excess of carbon, as it cannot be 

 employed to form a part of any organ, is 

 deposited in the cellular tissue in the form 

 of tallow or oil. 



At every period of animal life, when there 

 occurs a disproportion between the carbon 

 of the food and the inspired oxygen, the 

 latter being deficient, fat must be formed. 

 Oxygen separates from existing compounds, 

 and this oxygen is given out as carbonic acid 

 or water. The heat generated in the forma- 

 tion of these two products contributes to 

 seep up the temperature of the body. 



Every pound of carbon which obtains the 

 oxygen necessary to convert it into carbonic 

 acid from substances which thereby pass 

 into fat, must disengage as much heat as 

 would raise the temperature of 200 Ibs. of 

 water by 70, that is, from 32 to 102. 



Thus, in the formation of fat, the vital 

 *orce possesses a means of counteracting a 

 deficiency in the supply of oxygen, and con- 



