152 MILK. 



insoluble in water will consist of fats. The soluble 

 portion will contain lactic acid (q. v.). 



5. Dry a portion of fresh lymph at 100 C., powder 

 the residue, and burn to a white ash. Examine the 

 ash : it will contain sulphate, phosphate, carbonate, 

 &c., of the alkalies, and a small quantity of earthy 

 salts. Notice prevalence of soda over potash salt. 



Melanine. The black pigment of the eye or of mela- 

 notic cancers must be isolated as much as possible, 

 and purified by solution in ammonia and precipitation 

 by hydrochloric acid. It will possess a composition 

 similar to uromelanine (q. v.) 9 but different properties. 

 A portion will be found to be quite insoluble in any 

 ordinary reagent. 



Milk. 1. Milk has a specific gravity 1*018 to 

 1-045. 



2. Test the reaction with litmus paper ; the reaction 

 is usually alkaline. 



3. Examine some milk under the microscope ; it will 

 appear as a clear liquid, in which float the milk 

 globules. These vary in diameter from about 0'0012 

 to 0-0030 inch. 



4. Add a little acetic acid to milk ; the globules will 

 become distorted. 



5. Shake up some milk with ether; the globules; 

 though they consist of fat, are not dissolved. This is 

 due to the fact that each globule has an envelope 

 which is insoluble in ether. 



6. Shake up some milk with caustic potash, which 



