342 CONSIDERATION OF CARBON COMPOUNDS. 



facilitates precipitation, whilst strongly alkaline solutions are 

 not precipitated by heating. (The presence of too much acid 

 may also prevent precipitation.) During the coagulation some 

 sulphuretted hydrogen is generally liberated, indicating a de- 

 composition. 



Coagulated albumin is dissolved by strong solutions of alka- 

 line hydrates; compounds of albumin with an alkali, so-called 

 alkali-albumins, are found in vegetable and animal fluids. 



Albumin is also precipitated by picric acid, metaphosphoric 

 acid, and by mercuric chloride. 



Serum-albumin is the most abundant albuminous substance in 

 animal bodies, and may be obtained from blood (after having 

 separated the fibrin) by heating to 70, when it coagulates. It 

 is an almost white, or pale yellow, elastic substance. Pathologi- 

 cally it occurs in urine. 



Egg-albumin differs but little from the former, but may be dis- 

 tinguished from it by being coagulated by ether, which does not 

 affect blood-albumin. It exists in solution in the white of eggs, 

 where it is contained in a network of delicate membrane. 



The yolk of egg contains a substance in solution called vitelin, 

 an albuminous substance containing also phosphorus; it is 

 probably a mixture of albumin and casein; it is precipitated by 

 heating to 75-80, or by alcohol, which latter decomposes it 

 into albumin and lecithin, a peculiar glyceride containing phos- 

 phorus, but no sulphur. 



Vegetable albumin exists in nearly all vegetable juices, and is 

 the most valuable constituent of vegetables used as food. It is 

 coagulated at 61-63, and by nearly all acids. 



Blood-fibrin is found in the blood, chyle, lymph, and in many 

 serous exudations; it coagulates (clots) as soon as the blood 

 leaves the organism, and may be obtained from coagulated 

 blood by whipping with a bundle of twigs, and washing the 

 separated fibrin with water. It is, when recently obtained, a 

 white, gelatinous, tenacious mass, consisting of numerous mi- 

 nute fibrils; when dried it becomes hard and brittle. It is in- 



