DETERMINATION OF GLYCOGEN. 1399 



equal volume of 95 per cent alcohol. The precipitate is then trans : 

 f erred to a weighed filter, thoroughly washed with 50 per cent alcohol, 

 with absolute alcohol, and finally with ether, and dried to constant 

 weight at 100. 



The starch determinations for this bulletin were made by Mr. C. H. 

 Vosburgh. 



DIASTASE METHOD. a 



The diastase method, as well as Maercker's method, and methods 

 depending on the solubility of the starch in an autoclave, are not appli- 

 cable according to the experience of this laboratory to the determina- 

 tion of starch in meat. Mr. Munson employed the diastase method 

 in the examination of a series of sausages which were known to con- 

 tain a small amount of starch (due to the spices present), and obtained 

 less reduced copper than in a blank determination with diastase solu- 

 tion alone. This was undoubtedly due to the presence of interfering 

 substances which prevent the complete precipitation of the suboxid. 



AMBUHL'S METHOD. b 



From 2 to 10 grains of the meat under examination, according as it 

 is finely or coarsely subdivided, are thoroughly macerated with fifty 

 times their weight of water, boiled for 30 minutes, and diluted to 

 100 cc for each gram of meat employed. A portion of the clear liquid 

 is cooled, treated with iodin, and the depth of color compared with 

 solutions containing a known amount of the same kind of starch boiled 

 for the same length of time. 



This method gives results that are only roughly approximate, but 

 it is of value because of its convenience. 



DETERMINATION OF GLYCOGEN. d 



Niebel e has recommended that the percentage of glycogen be used 

 as the criterion in the detection of horse meat. He suggests that meat 

 which is found to contain more than 1 per cent of glycogen in the dry 

 fat-free -substance be considered horse meat. Later investigations go 

 to show that this determination can not be used alone for the detection 

 of horse meat, since immediately on the death of the animal the gly- 

 cogen begins to decompose, owing to the ferments present. At the 



a Amthor, Rep. Anal. Chem., 2, 356; U. S. Dept. of Agric., Chem. Div. Bui. 46, p. 25. 



b Pharm. Centralhalle, 1881, 22, 438; abs. Ztschr. anal. Chem., 1882, 21, 436. 

 ' c Two grams are sufficient where the entire sample is thoroughly macerated as 

 directed under Preparation of Sample, p. 1393. 



d By far the larger part of the glycogen determinations given in the tables were 

 made by Mr. Hay wood by the method described on page 1401. The others were 

 made by the writer, using the modification of the method of Pfliiger and Nerking 

 described on page 1402. 



e Ztschr. der Fleisch-u. Milch. Hyg., 185, 210. 



