ANATOMICAL APPEARAXCE. 377 



needful, as in all cases where urea is present its unstable nature 

 is, Avhen the examination of the urine is deferred, apt to lead 

 to incorrect conclusions in the matter of its composition, and 

 the extent to which this particular compound is present. In 

 density it is generally high. The colour has often been re- 

 ofarded as due to blood, or the colouring matter of blood. Ex- 

 amination with the microscope, however, fails to detect the 

 existence of either entire or broken-up blood-globules. The 

 solidification which the urine undergoes on the addition of 

 nitric acid, which has often been deemed indicative of the 

 existence of albumen, is, so far, a mistake, being due evidently 

 to the formation in excess of nitrate of urea, and the absence 

 of albumen is further confirmed by the non-coagulation of the 

 hquid on the application of heat. If albumen does exist, it is 

 certainly not in the form generally met with either in the blood 

 or urine. 



The crystals of the nitrate of urea may be easily produced 

 and examined by placing a little of the urine on a glass slide 

 or in a watch-glass, and either adding an equal quantity of 

 pure nitric acid to this, or first rendering the urine more con- 

 centrated by heating previous to the addition of the acid, 

 when the dark-coloured, rhomboid crystals of the nitrate 

 will show themselves in a few minutes. It is to the dark- 

 coloured urea, or rather the salts of urea, that the urine in 

 bulk chiefly owes its alteration in colour rather than to the 

 colouring matter of blood ; although there are instances where 

 this has been encountered, as also granular matter and epi- 

 thelial cells from the urinary tubes. These latter can only be 

 considered as adventitious, and are certainly not characteristic 

 of this disease. The dark colour and excessive quantity of 

 urea present in the urine is, as a rule, most readily detected at 

 the commencement of the disease. This is, however, not 

 invariable ; for if carefully observed, it may be noticed that in 

 many cases in the earlier stages of the disease, and while the 

 constitutional disturbance is most marked, and the animal 

 exhibiting much pain, the urine is comparatively little altered, 

 and that not until the pain is alleviated, and the systemic dis- 

 turbance less evident, does it put on its peculiar and distinc- 

 tive physical and chemical characters. 



Without the body, and probably also in its natural conduits. 



