CHEMICAL BASIS OF THE ANIMAL BODY. 115 



supply of carbohydrate food. It might more probably have been 

 expected that they should be shielded as far as possible from any 

 avoidable excessive digestive labour by the presentation of a directly 

 assimilable sugar. We cannot as yet offer any other explanation 

 of the observed facts, than the one that since lactose is incapable of 

 direct (alcoholic) fermentation, not only is the milk while it is 

 accumulated in the breast less liable to fermentative decomposition, 

 but also the tendency to fermentative disturbance in the alimentary 

 canal of the young animal is largely diminished. Both saccharose 

 (cane-sugar) and maltose 1 are similarly not directly fermentable and 

 both again in the adult are apparently converted into fermentable 

 dextrose during, or at least, immediately before absorption. The 

 subject is one which requires further investigation. 



FATTY ACIDS AND FATS, THEIR DERIVATIVES 

 AND ALLIES. 



I. ACIDS OF THE ACETIC SERIES. 



General formula C n H 2w+1 . COOH (monobasic). 



This, which is one of the most complete homologous series of organic 

 chemistry, runs parallel to the series of monatomic alcohols. Thus 

 formic acid corresponds to methyl alcohol, acetic acid to ethyl (ordi- 

 nary) alcohol, and so on. The several acids may be regarded as being 

 derived from their respective alcohols by simple oxidation taking 

 place in two stages, the first yielding an aldehyde the second an acid 

 by direct union of oxygen with the aldehyde 2 . Thus with ethyl alcohol 



(i) CH 3 . CH 2 . OH + O = CH 3 . COH + H 2 O, 

 (ii) CH 3 . COH + - CH 3 . COOH. 



The successive members differ in composition by CH 2 , and the boiling 

 points rise successively by about 19C. Similar relations hold good 

 with regard to their melting points and specific gravities. The acid 



1 Horace Brown. Private communication to author. Cf. v. Mering, Zt. f. 

 physiol Chem. Ed. v. (1881), S. 189. 



' 2 The views as to the possible importance of the aldehydes have already been 

 referred to when treating of proteids (see p. 51). It is further interesting to notice 

 that a simple polymerisation, to which it is very prone, of the lowest (meth-) 

 aldehyde H . COH, would yield a substance having the composition of a carbohydrate. 

 This is indeed a view which is held by many as to the mode of formation of starch 

 in plants. Cf. Miller's Chemistry, Part in. 1880, Sec. 1, p. 726. 



h 2 



