DEFINITIONS AND TECHNICAL CONSIDERATIONS. 365 



glands that excrete with the organs that secrete. For example, at certain 

 periods at the end of gestation certain glands forming part of the udder ex- 

 crete a fluid called colostrum (rich in salts and albumin). This had pre- 

 viously been a yellowish mucus, later was made up of a series of fat or milk 

 globules, and changed its condition just previous to the birth of the progeny. 

 The fat globules do not hold together, and later, when the actual milk has 

 been secreted, the colostrum globules disappear to be replaced by regular milk 

 globules, surrounded by a thin covering of casein, that are very numerous 

 until the calf is weaned. All milk, whatever be its source, contains enough 

 nutrients to sustain life. 



The evaporation from the body or perspiration is one of the most important 

 forms of excretion, and is more complicated than many suppose. Besides 

 watery vapor, carbonic acid, acetic and lactic acids, certain special organic 

 and inorganic substances are present, sodic chlorid, phosphates, etc., being 

 found among the latter. The oily matter thrown oft' through the skin is ex- 

 creted by special glands. Jn a full-grown ox, this excretion attains consider- 

 able proportions. Experiments of Henneberg and Hohmann show that this 

 water evaporation through lungs and skin can reach 22 pounds per diem. 

 During this excretion very little nitrogen escapes in the same direction. On 

 the other hand, Grouven shows that considerable ammonia is thrown off. 

 The carbon escapes mainly through the lungs, but much is also excreted 

 through the skin in the form of carbonic acid, as previously mentioned. The 

 hydrogen combining with oxygen is eliminated mainly in the form of water. 

 The most important excretion of the body is done by the kidneys through 

 which the blood passes. In these the nitrogenous substances formed by the 

 decomposition of the albumin of the body are removed. The secretions from 

 the kidneys are received in the bladder before being expelled from the body. 

 The most important element in the urine of cattle is urea, a substance very 

 rich in nitrogen, also hippuricacid which corresponds to uric acid in carnivor- 

 ous animals, the inorganic substances being alkaline bi-carbonates. Phos- 

 phoric acid appeai-s to be absent from the urine of cattle. Urea is rapidly 

 eliminated from the blood in a healthly animal under which circumstances it 

 is not deposited. When the deposit does occur, there is something faulty in 

 the working of the organs, and complications, such as rheumatic gout, are sure 

 to follow. In a good healthy full-grown animal the amount of urea thrown 

 off per diem attains about one pound in weight. 



Urea crystallizes easily and is soluble in water. During the phenomenon 

 of osmosis, these crystals pass in and out with great ease. Henneberg says 

 that the 33.5 parts of nitrogen contained in 100 parts of anhydrous albumin 

 may be separated as urea. The remaining albumin combines with 12.3 parts 

 water to form 51 .4 parts fat and 27.4 parts carbonic acid. The amount of urine 

 excreted varies very much with the animal and the kind of food used, some 

 individuals having greater power of assimilation than others. Upon general 

 principles, it may be admitted that the richer the fodder is in protein sub- 

 stances, the greater will be the quantity of nitrogen in the urine. Protein 

 substances when fed in excess of actual requirements should be eliminated 



