212 CONJUGATED ACIDS. 



of calves, while still sucking, (compare p. 195.) The peculiar 

 urine of birds, both carnivorous and granivorous, and of ser- 

 pents, (which, as is well-known, is generally discharged with the 

 solid excrements, although in snakes it is often unmixed with the 

 latter,) consists almost entirely of urates. In the urine of tortoises 

 uric acid has been found by Marchand* and myself, and Taylorf has 

 discovered it in urinary calculi from the Iguana. That the red 

 excrement of butterflies consists essentially of alkaline urates, and 

 that the excrement of many beetles contains the same substances, 

 has been long known ; I have, however, not only found uric acid 

 in the excrements of many larvce%, but also in large quantities in 

 those vessels of larvae, to which comparative anatomists have applied 

 the name of biliary vessels. 



It is well-known that the substance called guano is produced 

 from the excrements of sea-birds ; and that it is found not only in 

 the islands of the South Sea (especially in the neighbourhood of 

 Chili,) but also on the coast of Africa and even in England. 



In the urine of the lion, Hieronymi found only 0'022$ of uric 

 acid, and Vauquelin could find none whatever. 



The nature of the food exerts far less influence on the amount 

 of the uric acid which is secreted than on that of the urea. While 

 living on a mixed diet I|| discharged on an average 1*1 gramme of 

 uric acid in 24 hours, while during a strictly animal and a strictly 

 vegetable diet, the respective amounts were 1*4 and TO grammes. 



As the activity of the skin can to a certain degree replace that of 

 the kidneys, it is easy to understand how an increased activity of 

 the skin may cause a diminution of the uric acid in the urine ; 

 hence it was that Fourcroy^f found that the urine of a man con- 

 tained more uric acid in winter than in summer, and that Marcet** 

 was led to the conclusion that the uric acid diminishes in the urine 

 after severe perspiration. Schultensft found that in Holland, 

 where, in consequence of the great humidity of the atmosphere, the 

 cutaneous transpiration is diminished, the amount of uric acid varied 

 from 0'21 to 0*67; for a similar reason, in tropical countries, 

 lithiasis is altogether unknown. These observations, however, 



* Journ. f. pr. Ch. Bd. 35, S. 244-247. 



t Phil. Mag. vol. 28, pp. 36-46. 



Jahresb. d. phys. Ch. 1844. S. 25. 



Jahrb. de Ch. u. Phys. Bd. 3, S. 322. 



|| Journ. f. pr. Ch. Bd. 25, S. 254. 



IF Syst. de Connaiss. chim. T. 10, p. 236. 



"* An Essay on Calculous Disorders, 1817, p. 176. 



tt N. Gehlen's Journ. Bd. 3, S. 4. 



