THE NITROGEN COMPOUNDS 53 



When macerated beef is treated with cold water the 

 albumin in it goes into solution, and if this extract is 

 boiled the albumin separates in clotted masses. 



The clear serous fluid that is left after removing the 

 clot from blood contains albumin. After the casein is 

 removed from milk by acid or rennet, the albumin of the 

 milk remains in the whey. It is this which in part causes 

 milk to clot if brought to the boiling-point. As stated, one 

 example of this class of proteins is the white of an egg, 

 which, when cooking in boiling water, becomes a hard, 

 coagulated mass. Albumin in the serous fluids and in 

 blood is called serum-albumin; in milk, lact-albumin, and 

 in eggs, ova-albumin. 



A small proportion of the proteins of plants is found to 

 be albumin; for instance, Osborne found .3 to .4 per cent 

 in wheat, .43 per cent in rye, .3 per cent in barley, .5 per 

 cent in soja-beans, and some in most seeds. This possesses 

 essentially the same characters as the animal albumin 

 described previously. Whenever a vegetable substance 

 is leached with water, it is probably this protein which 

 would be the first to suffer removal or destructive 

 fermentation. 



67. The globulins. These proteins are usually asso- 

 ciated with albumins. When animal tissues are treated 

 with water, but a small part of the proteins dissolve. If, 

 however, we add to the water a mineral salt, especially 

 common salt (sodium chloride), sufficient to secure a 

 10 per cent solution, an additional and considerable 

 amount of protein may be extracted. Certain compounds 

 so extracted are called globulins, and differ from the 

 albumins in being practically insoluble in pure water and 

 in a saturated solution of certain mineral salts, such as 

 sodium chloride. The so-called globulins form an impor- 



