18 ORGANIC CONSTITUENTS. 



Albumen always contains more or less salts, pliospliate and 

 sulphate of lime, cliloride of sodium, and probably some lactates. 

 Their amount is variously estimated by difiPerent chemists : the 

 average is about 4 to 8^. 



In the albumen of the egg INIulder found 0'3g, and in 

 that of l)lood, 0-4^ of sulphate of lime. 



The development of the young animal in the egg of the 

 bird during incubation affords a striking illustration of the 

 physiological import of this substance. It is easily shown that 

 the egg contains no nitrogenous compound except albumen. 

 The albumen of the yelk has been proved, by the analyses of Bence 

 Jones and Scherer, to be identical with the albumen of the 

 white ; and in addition to this the yelk only contains a yellow 

 fat with traces of iron. Yet we see in the process of incuba- 

 tion, during wdiich no foreign matter, except atmospheric 

 air, can be introduced, or can take any part in the development 

 of the animal, that feathers, claws, blood-corpuscles, fibrin, 

 cellular tissue, and vessels are produced. 



Diagnosis of albumen. It coagulates at 167°. It is not 

 precipitated by acetic or dilute sulphuric acid, and from these 

 acid solutions it is precipitated by ferrocyanide of potassium. 

 Corrosive sublimate and nitric acid throw down copious de- 

 posits. 



3. Fibrin. 



This modification of protein occurs in two forms, dissolved 

 and coagulated. The former occurs in blood, lymph, chyle, 

 juices of plants, &c., as long as these fluids form a part of the 

 li\'ing organism ; on their w ithdrawal from the influence of the 

 vital force, the fibrin speedily coagulates. It is found in both 

 these states in the animal and vegetable kingdoms. 



The best method of obtaining it for chemical examination is 

 either by briskly stu'ring newly-drawn blood with a little bun- 

 dle of twigs, or else by shaking it in a stoppered bottle with a 

 few bits of lead or tin. The fibrin adheres to these substances 

 in the form of a nearly colourless coagulum. This must be 

 washed in cold water till it ceases to give oft' any colour what- 

 ever ; it must then be treated with boiling ether, in order to 

 remove the fat w^hich is always associated with it. 



When dried, it assumes a pale yellow colour, is devoid of 



