62 PROTEINS. 



in milk, but in larger amounts in colostrum. Crowther and 

 Eaistrick find that it is identical with serum-globulin. Its chief 

 characteristic is its solubility in sodium chloride solutions even 

 when acidified. 



Storch's Mucoid Protein. The following properties are 

 given by Storch : Washed with alcohol and afterwards with 

 ether, and dried in air at the ordinary temperature, it forms 

 a loose, fine, hygroscopic powder of a greyish-white colour. It 

 is insoluble in dilute ammonia and acetic or hydrochloric acids ; 

 it swells considerably without dissolving in weak solutions of 

 alkalies, and is only partly soluble in dilute potassium or sodium 

 hydroxide. It gives the reactions of proteins i.e., red color- 

 ation with Millon's reagent, brown colour with iodine and yellow 

 with nitric acid and ammonia (xantho -protein reaction). When 

 heated with dilute hydrochloric acid it yields a substance which 

 reduces Fehling's solution ; the amount of copper reduced is 

 6-5 parts for each 100 parts of dry ash-free substance. It gives 

 also the biuret reaction. 



It contains 14-76 per cent, of nitrogen and 2-2 per cent, of 

 sulphur, of which only a small portion is removed by boiling 

 with alkalies. Abderhalden and Voltz find glycine among the 

 cleavage products, and the amounts of tyrosine and glutamic 

 acid differ from those in casein. 



It is not improbable that it is a mixture and contains proteins 

 of the cellular elements, milk cells, and other products from the 

 udder. 



Preparation of Mucoid Protein. (i.) The author has found 

 the easiest method is to centrifuge sweet butter milk and 

 wash the deposit several times with water made faintly alkaline 

 with ammonia, the deposit being separated each time by centri- 

 fugal action. The mass is treated with strong alcohol, and after- 

 wards with ether, and dried in vacuo. 



(ii.) Storch has prepared it from butter, by melting 1 to 2 Ibs. 

 at a low temperature ; the fat is carefully decanted ; and the 

 liquid rinsed twice with benzene, diluted with distilled water 

 and mixed with one and a half times its volume of strong alcohol. 

 The precipitate is washed with 60 per cent, alcohol and extracted 

 with ether till all fat is removed, and air dried. 



(iii.) Fresh cream (about 30 per cent, fat) is diluted with four 

 times its volume of a 33 per cent, solution of cane sugar and 

 placed in a large separating funnel ; after a day's repose, the 

 sugar solution is drawn off, and the remaining cream again 

 mixed with four times its volume of the sugar solution ; this 

 process is repeated four times and the washed cream is shaken 

 with an equal volume of strong alcohol, and twice as much ether 

 and some benzene are added. A gelatinous precipitate separates 



