76 CHEMICAL PHYSIOLOGY. 



(c.) Boil some water, and plunge into it any other muscle 

 of the same frog ; it is alkaline. 



(d.) Test the reaction of a piece of butcher's-meat. It is 

 intensely acid. 



(e.) Tetanise a muscle for a long time. Its reaction be- 

 comes acid. 



2. Watery and Saline Extracts. 



(a.) Mince some perfectly fresh muscles from a rabbit or 

 dog. Extract with water, stirring from time to time. 

 After half an hour, pour off, and filter the watery extract. 

 Re-extract the remainder with water until the extract gives 

 no proteid reactions. For the purposes of this exercise, half 

 an hour is sufficient. Keep the filtrate, which contains the 

 substances soluble in water. 



(b.) Take some perfectly fresh muscle from a rabbit, rub 

 it up with sand in a mortar, and extract it with a large 

 volume of 10 per cent, solution of ammonium chloride, 

 NaCl, or 5 per cent. MgSO 4 . Stir occasionally, and allow 

 it to extract for an hour. A stronger extract is obtained if 

 it be left until next day. Pour off the fluid, keep it as it con- 

 tains the substances soluble in saline solutions, the globulins. 



3. With the filtrate of 2 (a.) 



(a.) Test for proteids e.g., serum-albumin. 



(b.) Test the coagulating point of the proteids it contains 

 (45 and 75 C.) 



(c.) Add crystals of ammonium sulphate to saturation, 

 which precipitates all the proteids. 



4. With the filtrate of 2 (b.) 



(a.) Pour a few drops into a large quantity of water, 

 observe the milky deposit of myosin. The precipitate is 

 redissolved by adding a strong solution of common salt. 



(b.) Test the coagulating point. Four proteids are coa- 

 gulated by heat at 47, 56, 63, and 73 C., an albumose 

 being left in solution. The fluid is acid in reaction. 



