CH. XXXVII.] PATHOLOGICAL URINE 573 



red. Microscopic examination then reveals the presence of blood 

 corpuscles, and on spectroscopic examination the bands of oxyhsemo- 

 globin are seen. 



If only a small quantity of blood is present, the secretion 

 especially if acid has a characteristic reddish-brown colour, which 

 physicians term " smoky." 



The blood pigment may, under certain circumstances, appear in 

 the urine without the presenqe of any blood corpuscles at all. This 

 is produced by a disintegration of the corpuscles occurring in the 

 circulation, and the most frequent cause of this is a tropical disease 

 allied to ague, which is called paroxysmal hcemoglobinuria (Black- 

 water fever). The pigment is in the condition of methaemoglobin 

 mixed with more or less oxyhsemoglobin, and the spectroscope is 

 the means used for identifying these substances. 



Pus occurs in the urine as the result of suppuration in any part 

 of the urinary tract. It forms a white sediment resembling that of 

 phosphates, and, indeed, is always mixed with phosphates. The pus 

 corpuscles may, however, be seen with the microscope ; their nuclei 

 are rendered evident by treatment with 1 per cent, acetic acid, and 

 the pus corpuscles are seen to resemble white blood-corpuscles, which, 

 in fact, they are in origin. They dissolve in glacial acetic acid. 



Some of the proteid constituents of the pus cells and the same 

 is true for blood pass into solution in the urine, so that the urine 

 pipetted off from the surface of the deposit gives the tests for 

 albumin. 



On the addition of liquor potassae to the deposit of pus cells, a 

 ropy gelatinous mass is obtained. This is distinctive. Mucus treated 

 in the same way is dissolved. 



Arginine and Arginase. We have seen (p. 557) that arginine belongs to the 

 same class of substances as creatine. Creatine (methyl-guanidine-acetic acid) has 



NH ^ 

 the formula >C i - N(CH 3 )CH 2 COOH. On decomposition this takes up a 



molecule of water, and splits in the situation of the dotted line in the above formula 

 into urea ^R 2 / 00 ' and sarcosine NH(CH.j)CH 2 COOH (see also p. 563). The 

 formula for arginine differs from that of creatine on the right-hand side of the 

 formula, where the sarcosine group is replaced by that of diamino-valeric acid or 

 ornithine. The decomposition of arginine into urea and ornithine can be brought 

 about by a ferment called arginase (Kossel and Dakin) which occurs in the tissues, 

 especially in the liver. This is the first discovery of a urea-forming ferment. 



