CASEIXE. 47 



coagulated caseine, is a compound of caseine with phosphate 

 of lime. For if an acid be cautiously added, so as just to 

 neutralise the alkali, the milk remains liquid, but coagulates 

 on boiling, and this curd is like that from rennet, insoluble 

 in alkaline solutions, in which pure caseine is soluble. Ca- 

 seine is the proper ferment for the lactic and butyric fermen- 

 tation, as fibrine or gluten is for the vinous fermentation. 

 The caseine of peas and beans is obtained by rubbing up the 

 seeds with water, and allowing the starch to settle. \Ve have 

 then a solution of caseine, turbid, and, but for the absence of 

 butter and sugar, hardly to be distinguished from skimmed 

 milk. The Chinese make cheese from peas and beans, and 

 coagulate it by rennet This cheese, when it decays or putri- 

 fies, acquires the peculiar smell and taste which characterise 

 the cheese from milk in the same states. Fresh cheese is 

 tasteless, save for the butter in it ; but on keeping, oily acids, 

 such as butyric and valerianic acids, and ammonia, are slowly 

 formed, and hence the strong flavour of old cheese." 



The whole of the nitrogenous principles have a remarkable 

 affinity for the phosphates, and this is most useful in the 

 process of nutrition. Phosphates enter largely in solution 

 in milk, which is thus rendered fit nutriment for a young 

 animal requiring bone earth to harden its skeleton, and albu- 

 men performs the same office for the chick in ovo. 



There are many other substances in plants and animals 

 containing nitrogen, and a very remarkable group in the latter 

 may be classed under the head 'Extractive matters/ By this 

 we mean substances obtained besides all we have mentioned, 

 and which are soluble in water, but some also in water and 

 rectified spirit, and others likewise in pure alcohol. 



The gelatinous class of nitrogen-containing principles is a 

 very important one. Gelatine is the basis of the connective 

 and white fibrous tissue, and in a slightly modified form, as 



