EXCRETION 215 



of uric acid which the kidney can secrete. When uric acid is 

 in excess in urine, brown crystals of uric acid are deposited as 

 " gravel " soon after it is passed. Even when not in excess, 

 uric acid crystals appear after a sufficient time. In other cases 

 uric acid, when in excess, is thrown down in the form of a cloud 

 of acid urates of sodium and other bases, which renders the 

 urine turbid. These urates are redissolved when the water is 

 warmed. 



The more fortunate of human beings need never concern 

 themselves with the chemical history of uric acid. It is always 

 present in their body- fluids. It is excreted by the kidney. Its 

 formation is of no greater interest than that of creatinin and 

 other nitrogenous compounds which escape the almost universal 

 reduction to urea. Persons who have a uric acid diathesis are 

 in a very different plight. Every scrap of evidence bearing 

 upon its origin is of supreme importance. Unfortunately, the 

 evidence collected as yet is scanty, and its application for 

 remedial purposes impracticable. 



The only disease in which uric acid is invariably in excess is 

 leucocythaemia. This is a condition or habit marked by the 

 presence in the blood of a very great number of white blood-cor- 

 puscles and a paucity of red ones. The connection between this 

 disease and the production of uric acid is made plain by certain 

 experiments in diet. If flesh which contains relatively a 

 large proportion of cell-nuclei is eaten, the uric acid excreted 

 is markedly increased. Sweetbread, especially " neck sweet- 

 bread " i.e., thymus gland is a mass of comparatively small 

 cells with large nuclei. If thymus gland be substituted for 

 all other meaty foods, the quantity of uric acid appearing in the 

 urine is doubled. A large increase in the quantity of ordinary 

 meat or fish consumed also increases uric acid, because all 

 meat-fibres contain nuclei. If egg-albumin be taken instead 

 of meat, uric acid is not increased. A sudden excess of mus- 

 cular work leads to an increase in uric acid, owing presumably 

 to the unusual activity of the tissues. This used to be very 

 noticeable in the case of young men during the first few days 

 of " training " under the old system ; but it may have been 

 due to the generous consumption of chops and steaks, rather 

 than to the increase in physical work, and consequent destruc- 

 tion of tissue. Nuclei contain nucleo-proteins, which split into 



