BY DR. LAUDER BHUNTON. 443 



boiling; by giving with acetic acid a precipitate which shrinks 

 together in pure acid, instead of swelling and dissolving as 

 albuminous bodies do. The addition of potassium ferrocyanide 

 to the acetic acid prevents it from precipitating mucin, so that 

 no turbidity is produced unless albuminous substances are also 

 present. It gives no precipitate with mercuric chloride; when 

 heated with liquor potassie and cupric sulphate, the solution 

 remains of a clear blue. 



Preparation, (a) From Salivary Glands. Wash the sali- 

 vary glands of an ox or sheep well. Cut them up into small 

 pieces. Wash away any remaining blood with a little water. 

 Mix the glandular substance well up with a considerable quan- 

 tity of water, and filter through linen. Add acetic acid gradu- 

 ally to the filtrate, till a precipitate partly fibrous and partly 

 flocculent is obtained. Filter through linen. Wash the pre- 

 cipitate with water, and then with alcohol and ether, to remove 

 the fat. 



(b) From Tendons. Free the sinews of the legs of an ox or 

 sheep from muscle. Wash them well, and cut them up in small 

 pieces. Extract them with water. Put them into a large quan- 

 tity of lime or baryta water, and let them stand in a closed ves- 

 sel for several days. Filter. Add acetic acid in excess to the 

 filtrate to precipitate the mucin. Wash the white flocculent 

 precipitate with dilute acetic acid and then with dilute alcohol. 



(c) From Ox Gall. (See 134). 



Solubility. 1 . Water : It does not dissolve, but swells very 

 much; \\.en the mixture is filtered, part of the mucin often 

 passes tlirough, forming a turbid filtrate. The mixture with 

 water is not tenacious, and no foam is produced on shaking it. 

 2. XaCl solution. Add a little solid NaCl to a mixture of 

 mucin and water. It will become clearer. Put a glass rod into 

 the liquid. It will now be found to be tenacious, and on with- 

 drawing the rod a" long thread will follow it from the fluid. 

 Shake it, and foam will form. Add a large quantity of water 

 to the solution or mixture (for it is not certain which it is), and 

 the mucin will be precipitated. 3. Very dilute hydrochloric 

 acid of less than 1 per cent., or other mineral acid, does not dis- 

 solve mucin. 4. Dilute hydrochloric acid of 5 per cent, parity 

 dissolves it. Shake the solution and it foams. Add a little 

 NaCl to it, and the mucin will dissolve much more readily. 

 5. Concentrated hydrochloric, or other mineral acid, dissolves 

 it completely. 6. Liquor potassrc dissolves it; add a little to 

 some mucin, but not enough to dissolve the whole of it. Filter. 

 The filtrate is not tenacious, and is neutral. 7. Baryta and 

 limewater dissolve mucin, and when used in small quantity 

 give, like liquor potass;c, a neutral filtrate. 



Precipitation of Mucin. f 1. Boil the neutral or slightly 

 alkaline solution. It will not be altered. 



