UREA. 165 



both of nitrate and oxalate of urea, which were made according to 

 Schmidt's method under the microscope, exactly coincided with 

 the measurements given by Schmidt for these crystals. 



StrahPs method, which I have repeatedly tried, and which con- 

 sists in the extraction of the urea from four ounces of blood by the 

 addition of alcohol, and in diagnosing the existence of urea from 

 the crystallisation of the oxalate, does not appear to me to be 

 sufficiently conclusive ; for, in the first place, the quantity of urea 

 in four ounces is very small, even for microscopic observation ; 

 secondly, alcohol extracts from the blood certain organic matters 

 which partly separate on evaporation ; thirdly, oxalic acid always 

 precipitates mineral matters which render the object indistinct ; 

 and, finally, if its crystals be not crystallographically determined, 

 it is often very hard to distinguish oxalate of urea from crystallised 

 alkaline oxalates ; all of which reasons led me to think that Strahl's 

 experiments required to be confirmed in some other manner. 



Urea increases abnormally in the blood of persons suffering 

 from degeneration of the kidneys,wherebythefunction of those organs 

 is destroyed. Under the general term of Bright' *s disease, we usually 

 include the various conditions in which there is a mechanical disturb- 

 ance of the urinary secretion, however different the histological alter- 

 ation in the renal tissue may be ; and we use the word uraemia to 

 indicate the group of symptoms which depend on the retention of 

 urea in the blood. 



Christison* was the first who recognised the occurrence of urea 

 in fc the blood in this disease. In any other disease, urea is only 

 rarely found in the blood ; hence, it is by no means requisite that 

 the symptoms of ureernia should be combined with the presence of 

 urea in the blood, since every physician knows how often Bright's 

 disease occurs without this group of symptoms ; it is only when 

 the urine is very scanty that these symptoms occur: that of vomiting 

 is not by any means a necessary one, as is generally supposed. 

 Moreover urea has been found by Raineyt and Marchand, in the 

 blood of cholera patients, but only when there was ischuria ; and 

 GarrodJ thinks that he has found it in the blood of a gouty 

 patient. 



Rees and Wohler|| have detected urea in Liquor Amnii, which, 



* On granular degeneration of the kidneys, &c. Edinburgh, 1839, p. 20. 



t Lond. Med. Gaz. Vol. 23, p. 518. 



J Op. cit. 



Lond. Med. Gaz. Vol. 23, p. 462. 



|| Ann. d. Ch. u. Pharm. Bd. 58, S. 98. 



