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(2) being a product of tlie deconipositioii of cellulose, it may possibly 

 be formed, together with other orgauic acids and gases, in the process 

 of fermentation of the cellulose in the alimentary canal. According to 

 either proposition the i)resence of citric acid would be traceable directly 

 or indirectly to the food. Although the weight of evidence seems to 

 be to the ettect that citric aciil when taken into the organism is rapidly 

 burned to carbonic acid and water, it is suggested that a transfer of 

 citric acid from the food to the milk is still conceivable, since in the 

 secretion of milk not the final products of decomposition but probably 

 the substance of tiie body itself is drawn ujion. C;irbohydrates are 

 also completely burned within the body, but milk-producing animals 

 separate a carbohydrate (milk sugar) in large quantities in the milk. 



The author proceeded to make exact determinations of the amount 

 of citric acid iu milk, according to a quantitative method devised bj- 

 himself, which is described in detail. This method depends upon 

 setting free the citric acid in the i)repared milk serum with 2h normal 

 sulphuric acid, dissolving the freed acid in alcoholic ether, separating 

 the milk sugar by crystallization, and linally precipitating the citric 

 acid (together with the sulphuric and phosphoric acids) with alcoholic 

 amnionia. The citric acid is determined in the final precipitate by 

 decomposing the ammonium citrate with a solution of bichromate of 

 potash, and measuring the carbonic acid evolved. The amount of citric 

 acid found in cows' milk by this method was 1.7 to 2 grams per liter — 

 a somewhat larger amount than llenkel found. 



With this exact method the author separated citric acid from human 

 milk also, the amount found being 0.54 grams per liter of milk, or less 

 than a third of that in cows' milk. 



After the presence of citric acid in goats' milk had been recognized, 

 feeding ex[)erinients were undertaken with goats to study the influence 

 of diflFcrent rations on the citric acid content of the milk. In diflerent 

 periods rations were led consisting respectively of (1) ordinaiy hay. (2) 

 brewers' grains, (3) beets and hay, (4) beets, oat straw, and linseed 

 cake, (5) clover hay, (0) black bread, (7) black bread, white bread, 

 and whe it Hour alternately, (S) hay and increasing amounts of citric 

 acid partially neutralized with sodium hulrale, and (9) jiea soup. The 

 latter ration, however, was only digested to a slight extent and was not 

 eaten readily, so that this jjcriod was partially a hunger period. The 

 results of these feeding exi)eriments lead the author to conclude that — 



(1) The citric-acid content of goats' milk is practically the same as 

 that of cows' milk, amounting with ordinary feetliug to from 1 to 1.5 

 grams per liter. Tlie variations from day to day on the same food were 

 not inconsiderable, and the i)ercentage of citric acid in the solids varied 

 even more widely. 



(2) The citric acid in milk is not derived from citric or other organic 

 acids containe<l in the fodder (hay, roots, etc.), for {a) it is contained iu 

 human milk, although in smaller amount ; {b) the feeding of increasing 



