STOMACH AND INTESTINE. 



387 



tially a species of fuel for that process of 

 calorific combustion,which pervades the whole 

 body, and which discharges its resulting car- 

 bonic acid by means of the respiratory func- 

 tion. And Liebig has adduced numerical 

 data from the fattening of animals, which lead 

 him to suppose, that these substances are 

 also capable of undergoing a process of de- 

 oxidation, that converts them into fat, and 

 thus enables them to augment the adipose 

 tissue. But this view rests on very insuf- 

 ficient foundations*: and is curiously con- 

 trasted with that oxidationf of hydro-carbons 

 into sugar, which the researches of various 

 recent observers seem to indicate as one of 

 the chief functions of the liver .J 



4. The importance of the ivater of the food 

 is such as justly entitles this liquid to the 

 rank of a fourth alimentary constituent. 

 For it forms about four-fifths of the entire 

 corporeal mass : and undergoes, at the va- 

 rious excretory surfaces of the skin, the lungs, 

 and the kidneys, a continual expenditure ; 

 the replacement of which is obviously neces- 

 sary to the maintenance of the proper com- 

 position of the body. 



The way in which this large aqueous con- 

 stituent facilitates the action of the various 

 organs is not very difficult to conjecture. 

 Their merely physical properties of hardness, 

 flexibility, and the like, often seem chiefly 

 determined by the quantity of the watery in- 

 gredient which they contain. And their far 

 more recondite vital properties seem quite as 

 immediately under its influence. Thus not 

 only do its solvent powers appear to be 

 eminently useful in furthering the minute 

 division, and the local transfer, of various 

 organic substances, but we are justified in 

 conjecturing that it gives a more specific 

 chemical assistance to many of those pro- 

 cesses of metamorphosis which are so inti- 

 mately connected with life. In both of these 

 respects, it would seem to afford a special aid 

 to the function of digestion. While that act 



* The increase of fatty matter supposed to have 

 been derived from these hydrates was calculated by 

 subtracting the fat added in the vegetable food 

 from the increase of the animal's weight ; this sur- 

 plus being set down as due to augmented adipose 

 tissue. Hence any error in estimating the fatty con- 

 stituent of this food, on the one hand or any neglect 

 to calculate the watery and proteinous constituents 

 of the increased adipose tissue, on the other would 

 partially account for the difference observed. And 

 it seems not unlikely that both of these inaccuracies 

 actually occurred in these observations. 



f Assuming that such a metamorphosis really- 

 obtained, it would not be difficult to explain most of 

 Liebig's results. For it is surely not impossible, 

 that the presence of an excess of sugar in the liver 

 might diminish the energy of this act; in other 

 words, that an excess of the product might lessen 

 the activity of the process. Thus the copious in- 

 gestion of sugar might check its formation, and 

 diminish the metamorphosis of the fat supplied to 

 the liver in the portal blood. And this retention 

 of the fatty fonn might not only affect the hydro- 

 carbons of the food, but also those which are pos- 

 sibly developed in the organism from its own pro- 

 teinous constituents. 



% Compare the remarks on the liver, at p. 401. 



of absorption, which conveys the dissolved 

 contents of the alimentary canal into the 

 surrounding veins, is greatly facilitated by 

 the heightened diffusive energy which the low 

 specific" gravity of water enables it to impart 

 to the fluids with which it has been mixed. 

 And finally, the use of water in relation to 

 the opposite extreme of nutrition namely, 

 to excretion may be well exemplified by the 

 urine, in which a highly poisonous product 

 of life is continually washed out of the system, 

 through the instrumentality of a stream of 

 this universal solvent. 



The details of death by thirst afford a 

 fearful commentary on the above remarks ; 

 although, from reasons which will presently 

 be mentioned, it will be obvious that even 

 these cases rarely afford us true examples of 

 the strict exclusion of all entry of water from 

 without the body. After a period of ago- 

 nizing thirst, the most distressing symptoms 

 of which seem to be referred to the dry and 

 inflamed throat and fauces, the deficiency of 

 water is gradually revealed by a diminution 

 which is almost a suppression of the various 

 secretions that normally contain a large pro- 

 portion of this liquid : namely, the sweat, the 

 urine, and the faeces. Increasing muscular 

 debility accompanies this change ; and is soon 

 followed by delirium and coma, ending in death. 



And, conversely, the benefits afforded by 

 water seem to receive an almost paradoxical 

 illustration from its effects in the opposite 

 states of starvation and of fattening. Thus, 

 as regards the latter process, animals are 

 stated to fatten much more easily and quickly 

 when allowed the free ingestion of this liquid. 

 And Becquerel and Lehmann state, that when 

 water is taken in excessive quantity, an in- 

 creased amount of urea is excreted from 

 the system of the healthy human subject.* 

 While the researches of Bidder and Schmidt-f- 

 show that, even after the withdrawal of all 

 other ingesta, the copious use of water con- 

 cedes to the starving animal a longer dura- 

 tion of life ; diminishing, not only the waste 

 of its protein compounds, but those collateral 

 results of the vital processes, which are ex- 

 emplified by the excretion of urea, carbonic 

 acid, and salts. 



Hence water, which forms about 85 per 

 cent, of the milk, is a universal constituent 

 of the food of animals; and varies only in the 

 proportion which its amount bears to that of 

 the solid ingredients mixed with it, or dis- 

 solved in it. In some of the lowest forms of 

 animal life, its relative amount is so great, that 

 the remainder of the food is only present in 

 the state of a very dilute solution. In cer- 

 tain aquatic creatures of this kind, the medium 

 around the animal seems to form a dilute 

 alimentary solution, which only requires an 

 act of absorption by the outer surface of its 

 body. And even in the higher animals, in 

 whom the other alimentary constituents are 



* An effect which is probably due to its favouring 

 the absorption of a larger quantity of protein from 

 the same amount of food. 



t Op. cit. p. 344. 



CC 2 



