MUCIN. NUCLEOALBUMINS. 53 



123. PREPARATION OF MUCIN. Mince finely a sub- 

 maxillary gland of an ox and extract it with water. Filter 

 and add to the filtrate strong hydrochloric acid until the 

 liquid contains 0.15 per cent, of acid, avoiding an excess. 

 The mucin is at first precipitated, but dissolves again upon 

 stirring. Then add two or three volumes of water, which 

 will precipitate it. Separate it from the liquid by filtration 

 or decantation and repeat the dissolving and precipitation 

 as before. Wash with water and, if the dry substance is de- 

 sired, with alcohol and ether. 



124. Try the solubility in calcium hydrate, and pre- 

 cipitate from this solution by acetic acid. 



125. Boil mucin for some time with dilute hydro- 

 chloric acid, and, after making the liquid alkaline, show 

 by Fehling's test that there is a reducing body present. 



126. Show that solutions of mucin in an alkali will 

 give the biuret test. 



THE NUCLEOALBUMINS. 



The nucleoalbumins occur widely distributed in the 

 animal and vegetable kingdoms, forming one of the princi- 

 pal constituents of protoplasm. They are found especially 

 in the cell, but sometimes in the secretions, such as the milk, 

 which contains casein. Some authors, however, include 

 in the class of nucleoalbumins only those found in the cell, 

 and exclude such as the casein of milk and the vitellin of 

 eggs. 



Chemically they are composed of the same elements 

 as albumin, but contain, in addition, phosphorus and some- 

 times iron. The}'' resemble in their properties the globu- 

 lins and alkali albumins. They differ, however, in contain- 

 ing phosphorus. They are also insoluble in neutral salt 



