ADVANCED CHEMICAL PHYSIOLOGY 



319 



into a porcelain crucible containing 4-5 gms. of plaster of Paris, stirred 

 and dried preferably in the oven (about 70 C.) for an hour. It is then 

 emptied into a small paper extraction thimble (4 cm. long), which is next 

 inserted into a short glass tube (2-5 x 7 cm.) with a number of holes in 

 the bottom and sides. This tube is connected with a reflux condenser 

 and the tube and cork (of the condenser) inserted in the 

 neck of a 150 c.c. extraction flask containing 20-25 c.c. 

 chloroform. Extraction is carried on for sixty minutes 

 on an electric hot-plate ; the chloroform is then made 

 up to some suitable volume, such as 20 c.c., filtered if 

 necessary, and then a colorimetric estimation is made. 

 5 c.c. of the chloroform extract is pipetted into a dry 

 test tube and 2 c.c. acetic anhydride (must be an- 

 hydrous) and 0-1 c.c. of concentrated sulphuric acid 

 are added. After thorough mixing the solution is 

 placed in the dark (and if necessary in a cool place. 

 Best temperature is 22 C.) for exactly ten minutes to 

 allow the colour to develop and then compared with a 

 0-005 per cent, aqueous solution of naphthol green B. 

 in a colorimeter, or, if preferred, with a standard pre- 

 pared simultaneously from pure cholesterol. If the 

 Duboscq instrument is used the cups should be re- 

 mounted in plaster of Paris as the chloroform dissolves 

 the balsam ordinarily employed. p IG . 202. 



Calculation. If the standard naphthol green B. solu- 

 tion be set at 15-5 mm. 0-4 mg. cholesterol treated as above will read 

 15 mm. 



Dil. of chloroform extract 



Standard in mm. 

 Unknown in mm. 



x o. 0004 x from 1 c.c. blood 



x 100 = cholesterol 



content of blood in per cent. Average is about 0-16 per cent. 



Determination of Fat in Blood may be carried out by the nephelo- 

 metric method (using either a nephelometer or a converted Duboscq 

 colorimeter) of Bloor (Jour. Biol Chem., 1914, 17, 377). 



CHAPTER XXIII 

 MUSCLE AND TISSUES 



Muscle constitutes one of the commonest foodstuffs, meat being 

 the form in which we take a large proportion of our protein and a 

 considerable amount of our fat. 



CHEMICAL COMPOSITION OF MUSCLE (APPROXIMATE) 

 Water ....... 75 per cent. 



Protein 20-21 



Extractives v 0-3-0-4 



Fat 2-3 



Salts . . . . . . . 1-0-1-3 



Proteins are most easily studied in an extract of muscle, which is best 

 prepared by killing a rabbit and, by means of a cannula tied into its 

 aorta, washing with normal saline until blood free. The muscles are 



