CHAPTER X 



SOME CONSTITUENTS OF URINE 



Occurrence of Growth- Substances {other than the auxins 

 and vitamins) in Urine 



Urine, in a heat below that of boiling water, yields a clear 

 liquor, of a very disagreeable smell, and which is found to 

 contain nothing saline. — Beaum6. 



A LARGE number of substances able to affect growth and 

 differentiation in plants are to be found in urine. Some of 

 them (auxin-a, auxin-b) probably pass unchanged through the 

 digestive tract, and, if they do, are integral plant-products. 

 Others are fission-products of plant or animal protein, the 

 latter being broken down either endogenously (in the body 

 processes of the excreting animal) or exogenously (in the 

 digestive tract, which is outside the body proper; or, less 

 commonly perhaps, as a result of eating decomposed food, 

 e.g., high game). Still another class is formed by those animal 

 hormones which are capable of excretion in urine ; of these the 

 sex hormones are the chief. 



In discussing urinary excretion, it should be borne in mind 

 that to speak of urine as if it were one material, is often 

 convenient, but does not always imply accuracy. The kind 

 and amount of substances naturally present in urines, or 

 excreted in urine after administration of a substance not a 

 foodstuff, vary widely with the species, sex, age, and idiosyn- 

 crasy of the animal. Thus, phosphates are abundant in 

 human urine, but are present in only small amounts in the 

 urine of horned cattle ; and hippuric and ornithuric acids, by 

 their very names, remind us of special occurrences. The 

 following outline should be read with such reservations, and 



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