DEFINITIONS AND TECHNICAL CONSIDERATIONS. 337 



The nervous tissue is the center of all the sensations of the body. All 

 organs receive from the nerves the impulse upon which they enter into activity, 

 and all voluntary and involuntary movements of the body are regulated by the 

 nervous tissues. Every perception of the senses is through the nervous tissue. 



Mucous tissue covers all the empty spaces in the interior of the body, the 

 digestive cnnal, the respiratory organs, etc. Its importance is very great dur- 

 ing every stage of the animal's development. A reasonable knowledge of this 

 question should be possessed by every farmer. 



The body of an animal consists mainly of nitrogenous elements, besides 

 which there is distributed through the tissues a certain amount of fat and non- 

 nitrogenous substances. After these are burned, there remains a residuum 

 which represents the mineral elements. It is interesting to pass these rapidlv 

 in review, remembering that the starting-point in cattle-feeding is to furnish 

 in the fodder those elements of which the body consists, so as to renew the 

 constant waste and build up new tissues. Experiments have long since demon- 

 strated that plants offer advantages not found elsewhere for this purpose. 

 Other experiments in digestion show what variety of plant gives the best result 

 in the physical laboratory of each kind of animal under consideration. 



(a) NITROGENOUS ELEMENTS. 



The main characteristics of plants is their high percentage of carbon; in 

 animals, on the other hand, the salient characteristic is the nitrogen. With 

 young and thin animals, nitrogenous substances constitute the principal part 

 of the dry matter of the body. The most important group of nitrogenous ele- 

 ments is the albuminoids or protein substances; these are met with under most 

 varied circumstances; they contain about 16 per cent, nitrogen, 7 per cent, 

 hydrogen, 54 per cent, carbon, 22 per cent, oxygen, and 1 per cent, sulphur. 

 They form the principal constituents of blood, eggs, muscular and nervous 

 tissue. ^Vhen dried in the soluble form, they are white or yellowish, without 

 smell and soluble in water; in the insoluble form they are insoluble in water. 

 By coagulation the soluble portions may be made insoluble. 



The most important of the group is albumen, found in all the liquids of the 

 animal's organism, more especially in the chyle and serum, the colorless por- 

 tions of the blood, and in the juice of meat or muscles. 



Fibrin is next in importance in the nitrogenous group; it is found either 

 liquid, dissolved in the blood, or in a solid state in the muscles. 



All these protein substances may undergo numerous transformations. It is 

 from them that all the other nitric elements originate, of which the body con- 

 sists, and in particular the gelatigenous substances. These are next in im- 

 portance to the albuminoids; they constitute the nitrogenous organic substances 

 of bones, cartilages, the greater portion of the tendons and ligaments. By 

 prolonged boiling these gelatigenous substances are converted into glue; they 

 contain less carbon than the albuminoids, and are entirely free from an organic 

 combination of sulphur when it exists its percentage is generally less than in 

 the albuminoids ; to them belongs a special group known as horny matter ; 

 they are found in the outer portions of the body, a thin layer upon the skin, 

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