244 MANUAL OF AGEICULTUEE. 



to form water, whence tliey are often termed carbo-liyclrates. In 

 Eoscoe's Chemistry they are arranged under the heads of Sue- 

 roses, CjoHgoOj;^, represented by sucrose or cane sugar; Glucoses, 

 CgH^gC^c represented by dextrose or grape sugar ; and Amyloses, 

 CgHj.Og, represented by dextrin, starch, cellulose, and gum. The 

 amyloses are insoluble in water, but the action of certain acids 

 converts them into dextrose, which is soluble in water; although 

 not to the same extent as is sucrose. Gum and cellulose are with 

 difficulty converted into dextrose ; starch, less so. Starch, how- 

 ever, soon assumes a soluble form under the action of the saliva 

 and other juices of the body. The action of the organic com- 

 pound diastase, which is always found present in seeds beginning to 

 germinate, renders starch stored up in the seed soluble for the use 

 of the embryo at that stage. The starch first assumes the properties 

 of dextrin, and then it is readily changed to dextrose. It will be 

 noticed that the addition of one molecule of water to those of the 

 third division will make them assume the same formula as those 

 of the second. 



The composition of the oleaginous compounds is the same, but 

 with the amount of hydrogen much in excess of the proportion 

 necessary, with the contained oxygen to form water. Conse- 

 quently, they are styled hydro-carbons. Glycerin, CgHgOg, is the 

 base of all fatty compounds, which vary with the different pro- 

 portions of acids in combination with it. Most fats and oils con- 

 tain a mixture of all these. The three principal acids are — 

 palmitic, C^gHg^Og ; oleic, C-^gHg^Og; and stearic, C^gllggOg. 



The albuminous compounds contain nitrogen, carbon, hydrogen, 

 oxygen, phosj^horus, and sulphur; they are also called the nitro- 

 genous compounds. The composition of them all varies but little; 

 and they are convertible by a slight rearrangement of atoms. 

 These compounds are derivable by animals only from vegetable 

 sources. They are assimilated without undergoing much alteration ; 

 and in the animal constitution have almost the identical com- 

 position as the relative compounds in plant life. The following 

 table shows the composition of the principal members of this 

 group which are met with in the animal body : — 



lUO'O 100-0 100-0 



Albumin and fibrin abound in blood and muscle. The glutin 

 of wheat corresponds to fibrin; and albumin is found in the 

 juices and seeds of plants. Casein is the albuminous compound 



