MEAT AND MEAT PRODUCTS. 18 



cent (by volume) alcohol, mix thoroughly, filter the mixture through an asbestus 

 filter and wash twice with a hot 4 per cent solution of potassium hydroxid in 50 per 

 cent alcohol. Then wash with 50 per cent alcohol until a small portion of the fil- 

 trate does not become turbid upon the addition of acid. Return the precipitate and 

 filter to the original vessel and dissolve the precipitate, with the aid of heat, in 60 cc 

 of a normal solution of potassium hydroxid. In the case of sausage with a hi-rh 

 starch content a somewhat larger volume of alkali may be required. Acidify the 

 filtrate strongly with acetic acid, dilute to a definite volume, thoroughly mix by 

 shaking, filter through a fluted filter, and precipitate the starch from an aliquot part 

 of the filtrate by means of an equal volume of 95 per-cent alcohol (sp. gr. 0.81) . Trans- 

 fer the precipitate to a filter, thoroughly wash with 50 per cent alcohol (by volume), 

 with absolute alcohol, and finally with ether, dry to a constant weight at the tem- 

 perature of boiling water, and weigh. 



9. DETERMINATION OF GLYCOQEN. 



The determination of glycogen has been suggested a as a means to detect the pres- 

 ence of horse meat. Recent results indicate that this determination is of limited 

 value because of the fact that glycogen begins to disappear soon after the death of the 

 animal and may entirely disappear after a short lapse of time. No definite conclu- 

 sions can therefore be derived from the results of this determination, but it is of 

 value as confirmatory. 



(a) QUALITATIVE METHOD. b 



Boil 50 grams of the macerated sample with 50 cc of water for from fifteen to thirty 

 minutes. Filter the broth through a moistened filter paper or piece of fine linen. 

 To a portion of the filtrate in a test tube add a few drops of a reagent composed of 2 

 parts iodin, 4 parts posassium iodid, and 100 parts water. In the presence of a large 

 percentage of horse meat the glycogen contained produces a dark brown color, which 

 is destroyed by heating and reappears on cooling. When starch is present it may 

 !>< precipitated by two volumes of glacial acetic acid, separated by filtration, and the 

 test for glycogen repeated in the filtrate. 



(b) QUANTITATIVE METHOD. 



The methods for the quantitative examination of glycogen are all tedious to the last 

 degree. Fairly satisfactory results may be obtained by the methods of Briicke, c 

 R. Ktilz, rt Pfliiger, e Hay wood, f and Pfliiger and Nerking. * Of these the last has been 

 selected as combining a sufficient degree of accuracy with the greatest simplicity and 

 convenience. 



Digest 50 grams of finely macerated meat on the water bath with 200 cc of 2 per 

 cent potassium hydroxid until solution is practically complete. Cool the solution, 

 dilute with water to exactly 200 cc, shake and filter. Treat 100 cc of the filtrate with 

 10 grams of potassium iodid and 1 gram of potassium hydroxid and stir until solution 

 is complete. Add 50 cc of 96 per cent alcohol, and allow to stand until the following 

 day. Then separate the precipitated glycogen by filtration, and wash with a sohil i< >n 

 containing 1 cc of 73 per cent potassium hydroxid, 10 grams of potassium iodid, 100 cc 

 of water, and 50 cc of 96 per cent alcohol (sp. gr. .81). Wash the glycogen with a 

 1 1 1 i x t tire of two volumes of 96 percent alcohol and one volume of water containing about 

 7 in-: of sodium chlorid JUT liter, dissolve in water, and remove the remaining traces 

 of proteids by the addition of double iodid of mercury and potassium. It is often 



Nii-l.-l. /tsdir. ang. Chem., 1895, 620. 



b Courlay and Corenmns. Ztsrhr. Ntilir. Ilyjr. Waar., 1896,1O, 173-174. 



SitzuiiK*iVr Anid. Wisscnscli.. Wicii, Bd. 63, II abth., 1871, p. 214. 



'/Ctsrhr. f. Biol., 4, 169. 



Arch. K-S. I'hysiol., 1899, 75, 120-247. 



Mour. Arn. chi-m. Soc., 1900, ii'i, S5. 



*Arch. Physiol., 1899, 76, 531-542. 



