125 



(juaiitities of citric aciil, amounting' in some cases to forty times the 

 ainouut given ott" in the milk, was accoini)anie(l by no increase of citric 

 a(M(l ill tlu' milk |)n)(liu'i'd; {<■) during' the feedinj; of bread, wheat thmr, 

 and pea meal, ''which surely contained nocitrie acid," the milk continued 

 to show the normal amountof this acid; aud (rf) when the animals were 

 fastinjj or when only a very limited (jnaiiMty of food was eaten, there was 

 no decrease noticed in the citric-acid content. 



(3) Citric acid does not come from the products of the fermentation 

 of cellulose in the alimentarj- canal of herbivora, for human milk con- 

 tains citric acid, and when bread, wheat Hour, or pea meal were fed, and 

 duriiifi^ fasting, the critic-acid content remained normal. 



The presence of citric acid in the milk given by fasting goats, is analo- 

 gous to the presence of milk sugar in the milk of carnivora receiving 

 food free from carboliy<lrates, and of fasting herbivora. When the 

 origin of milk sugar shall have been clearly shown, it may be possible 

 to secure some light as to the formation of citric acid from the other con- 

 stituents of the food or from the animal substance itself. 



Although these investigations furnish no definite answer to the ques- 

 tion as to the origin of the citric acid of milk, the author believes they 

 indicate that citric acid is a specific milk constituent, which, like the 

 casein, the glycerides of the volatile fatty acids in the butter fat, and 

 the milk sugar, is a product of the lacteal glands; but from what con- 

 stituents of the food or the body these ingredients, esj>ecially milk 

 sugar, are formed, it is at present im])Ossible to say with certainty. 



Volatile fatty acids in Holland butter, A. J. Swaving (Landw. 

 Vers. IStot., Si^pp. 127-141). — The author first briefly notices some of the 

 previous investigations made with a view to determining the intiuence 

 of food, period of lactation, etc., on the volatile fatty acids of butter. 



Thus, he states that in 1882 Muiiier* exainined samples of butter from 

 the vicinity of Amsterdam, during the whole year, and found that the 

 percentage of volatile fatty acids was lowest during the mouths of 

 October, November, December, and January. 



In 1888 Coster, Van ]Ioorn and Ma/uret examined butter made by 

 themselves each month of the year from the milk of a large number of 

 cows. They conclude from these studies that in the critical examina- 

 tion of butters the season of the year in which they were made should 

 be considered. 



The investigations of Cornwall and Wallace,]: in which examinations 

 were made of the butter produced by individual cows during a year, 

 showed no constant relation between the volatile fatty acids and the sea- 

 son, breed, age of animal, feeding, or time since calving. They give as 

 the average of 80 samples of butter, 13.C8 c. c. of tenth-normal alkali 

 for 2.5 grams of melted butter fat. 



•Zeitsch. f. aiialyt. Cheni., 82, p. 397. 



tS. vcrslag vau deu toestand der genieeute Amsterdaai gedureudo Let Jaar 1888. 



t Zeitsch. f. analyt. Chem., 1887, p. 317. 



