26 THE CHEMISTRY OF CATTLE FEEDING 



dextrine, maltose, and finally dextrose. This gradual hydrolysis 

 of starch can be effected by simply boiling for a long time 

 (several days) under a reflux condenser. The change takes 

 place much more rapidly in the presence of acids and alkalis, 

 especially the former. Starch is resolved into dextrose on 

 boiling with dilute acids for a few minutes. 



By the action of malt diastase at temperatures between 

 50 and 60 C., starch is converted into dextrine and maltose. 

 It is considered probable that dextrine is formed first, and 

 that maltose results from the subsequent hydrolysis of that 

 compound. At any rate, more dextrine and less maltose is 

 obtained at the higher temperature, and vice versa. The 

 proportion of dextrine to maltose in brewer's worts varies from 

 about one to two to equal parts. By prolonged action of 

 diastase dextrine is converted into dextrose. 



Similar changes conversion of starch into sugars are 

 also effected by many other enzymes, e.g. the ptyalin of saliva 

 and the pancreatic trypsin. Such changes are a condition 

 precedent to the absorption of starch by animals, and are 

 therefore of great physiological importance. 



Cellulose. The term " cellulose " is employed by botanists 

 to describe the material of which the cell wall, as apart from 

 the contents, is composed. It cannot, therefore, be regarded 

 as a single, definite, chemical compound, because the cell 

 walls of living organisms are in a constant, if gradual, state 

 of transition. Considered chemically, i.e. apart from their 

 pKysiological values, these changes take place mainly in the 

 direction of oxidation and dehydration. Cellulose first appears 

 in the plant in a highly hydrated colloidal form. By a series 

 of changes the obscurity of which is concealed under such 

 names as lignification, suberisation, degradation, etc. it is 

 converted into various organised structures of which cotton, 

 flax, jute, hemp, wood, cork, etc., may be taken as types. Of 

 these, cotton is the simplest. It has the composition and 

 properties of the typical cell wall, and will therefore be con- 

 sidered in detail. The others, which are also included in the 

 cellulose group, are most conveniently studied by comparison 

 with it. 



