SALIVARY CONCRETIONS. 571 



by the name of chalk stones. They are usually small, though it 

 is stated by Severinus that they have been observed as large as 

 an egg. It had long been the opinion of physicians, founded up- 

 on an alternation observed between the paroxysms of gout and 

 the passage of gravel in the urine, that these concretions were si- 

 milar to urinary calculi. Hence, after the discovery of uric acid 

 by Scheele, it was usual to consider the gouty chalk stones as 

 concretions of that acid. They were first subjected to a chemi- 

 cal analysis by Dr Wollaston in 1797, who found them compos- 

 ed of uric acid and soda. 



Gouty concretions are soft and friable. Cold water has little 

 effect on them, but boiling water dissolves a small portion. If 

 an acid be added to this solution, small crystals of uric acid are 

 gradually deposited on the sides of the vessel containing the so- 

 lution. They are completely soluble in potash when the action 

 of the alkaline solution is assisted by heat. 



When they are treated with dilute sulphuric acid or with mu- 

 riatic acid, the soda is separated, but the uric acid remains, and 

 may be separated by the filtre. When the liquid is evaporated 

 it yields crystals of sulphate of soda or of common salt, accord- 

 ing to the nature of the acid employed. The residuum possess- 

 es all the characters of uric acid. 



When uric acid, soda, and a little warm water are triturated 

 together, a mass is formed, which, after the surplus of soda is 

 washed off, possesses the chemical properties of gouty concre- 

 tions.* 



CHAPTER III. 



SALIVARY CONCRETIONS. 



SMALL concretions occasionally occur in the salivary glands, 

 especially the parotid and sublingual. These calculi were first 

 subjected to a chemical examination by Dr Wollaston, who 

 found them composed of phosphate of lime, associated with a 

 membranous substance. Fourcroy's analysis gave the same re- 

 sult. A small salivary concretion which I examined was com- 

 posed of phosphate of lime united to a membranous substance, 



* Wollaston, Phil. Trans. 1797, p, 386. 



