SOLID FATTY ACIDS. 105 



is indeed very considerable a fact long ago asserted by Berzelius,* 

 and directly proved by the experiments of Gay Lussac,t but whose 

 accuracy has been called in question by Liebig,{ yet I cannot 

 overlook the circumstance that the albuminous bodies, which are 

 never devoid of phosphate of lime, and often contain a large 

 quantity of it, afford far better means of transport for the bone- 

 earth in the animal body than lactic acid can do. 



How far my former view, that lactic acid is the most important 

 factor in the metamorphosis of the animal tissues, can still be 

 maintained, may be seen from the preceding observations. 



SOLID FATTY ACIDS. 

 =C m H m _ l O,.HO. 



FROM this formula it is obvious that these acids stand in a 

 close alliance with those which we have described in the com- 

 mencement of this work ; indeed, we have already associated 

 them with the latter in a single group, to which we have applied 

 the name of fatty acids ; but we meet here with the same diffi- 

 culties which present themselves in inorganic chemistry, in the 

 definition and classification of the metals. Nature recognises no 

 limits corresponding with our artificial systems, but for the 

 purposes of study a separation or arrangement is always useful, 

 provided it be not altogether at variance with nature. These fatty 

 acids have, however, certain essential characters, which distinctly 

 separate them from the first-named acids. Independently of 

 the high atomic weight of the acids we are now considering, and 

 of the circumstance that a very differently constituted group of 

 fluid acids is closely allied to them, the following are the 

 properties which characterise them as a special group. At an 

 ordinary temperature they are solid, white, and crystalline, 

 devoid of smell and taste, leave on paper a fatty spot which 

 does not disappear, are lighter than water, fuse below 100, can 

 only be distilled unchanged in vacua, are perfectly insoluble in 

 water, dissolve in boiling alcohol, and again separate from it in 

 crystalline forms as the solution cools, dissolve readily in ether, 

 decompose when heated in the air, and are inflammable; their 



* Lehrb. d. Ch. Bd. 9, S. 423. 



t Pogg. Ann. 13d. 31, S. 399. 



J Chemie in Anwendg. f . Physiologic. 



