THE URINE. 337 



or oxidation of certain bodies found in the animal organism, such 

 as creatin and uric acid. 



Urea is found most abundant in the urine of carnivora and man, 

 but in smaller quantities in that of herbivora. The quantity in 

 human urine is ordinarily 20-30 p. m. It has also been found in 

 the urine of certain birds and amphibians. Urea occurs in the per- 

 spiration in small quantities, about 2 p. m., and as traces in the 

 blood and in most of the animal fluids. It is also found in certain 

 tissues and organs, especially in the liver (in mammalia) and the 

 spleen, but not in the muscles. Under pathological conditions, as 

 in obstructed secretion of urine, the urea in the animal fluids and 

 tissues may increase to a considerable amount. Under these cir- 

 cumstances it may also occur in the muscles. 



The quantity of urea which is voided in 24 hours on a mixed 

 diet is in a grown man about 30 grammes, for women somewhat 

 less. Children void absolutely less, but relative to their body- 

 weight the excretion is larger than in grown persons. The physio- 

 logical significance of urea lies in the fact that this body forms in 

 man and carnivora, from a quantitative standpoint the most im- 

 portant nitrogenized final product of the metabolism of proteid 

 bodies. On this account the elimination of urea varies to a great 

 extent with the amount of proteid transformed, and above all with 

 the quantity of absorbable proteids in the food taken. The elimina- 

 tion of urea is greatest after an exclusive meat diet, and lowest, 

 indeed less than during starvation, after the consumption of bodies 

 free from nitrogen, for these diminish the metabolization of the 

 proteids of the body. 



If the consumption of the proteids of the body is increased, then 

 the elimination of urea is correspondingly increased. This is found 

 to a rather high degree in certain diseases with fever; also, though 

 to a less extent, after taking common salt or after abundant drink- 

 ing of water (Vorr). The elimination of urea is also somewhat 

 increased by several medicines; and lastly it is also increased after 

 poisoning with arsenic, antimony, and phosphorus, by the diminished 

 supply of oxygen as in severe and continuous dyspnoea poisoning 

 with carbon monoxide, hemorrhage, etc. In these cases an exact 

 difference has not always been made between the urea and the total 

 quantity of nitrogen in the urine, and it is just this last which is 



