740 PHYSIOLOGICAL CHEMISTRY. 



the latter be allowed to float on the mixture, a carmine-red ring will 

 form at the zone of contact, when the reaction is positive. 



It was formerly held that this test is pathognomonic of typhoid 

 fever. Later work has, however, shown that it usually is present in 

 typhoid fever and measles ; it is frequently present in erysipelas, 

 pneumonia, scarlet fever, diphtheria, and pulmonary tuberculosis ; it 

 is rarely present in acute rheumatic fever and cerebrospinal men- 

 ingitis. 



It is, however, of much value in the diagnosis of typhoid fever, and 

 is thought to indicate a bad prognosis in pulmonary tuberculosis. 



Functional tests of the kidney. Many attempts have been made 

 to find a substance which, when injected into the body, would be 

 excreted by the kidney in such a manner that examination of the 

 urine would show the ability of the kidneys to carry on their func- 

 tion of excretion. Among the substances tried are methylene-blue, 

 salicylic acid, and phloridzin. By far the most suitable substance 

 has recently been found in phenolsulphonephthalein (Geraghty- 

 Rowntree). This substance has no poisonous action, and is excreted 

 very rapidly by normal kidneys. It produces a red color in alkaline 

 solution, and its amount may thus be readily estimated by noting the 

 extent to which a standard solution must be diluted to produce the 

 same depth of color. It is somewhat more accurate to use a special 

 instrument, a colorimeter. After the injection of this drug (0.006 

 gramme) the unchanged drug will, under normal conditions, appear 

 in the urine in from five to eleven minutes, 50 per cent, is excreted 

 during the first hour, and from 60 to 80 per cent, during the first and 

 second hour together. 



In diseases of the kidneys the initial appearance is delayed and the 

 hourly output is decreased. 



Urinary deposits (sediments). Normal urine is always clear, but 

 occasionally, and particularly in abnormal conditions, it is turbid. 



Urine may be turbid when passed, and this indicates an excess 

 of mucus, or the presence of renal epithelium, pus, blood, chyle, 

 semen, bile, fat-globules, or phosphates or urate of sodium in excess, 

 etc. A turbidity subsequent to the passage of the urine is generally 

 due to the precipitation of phosphates or urates, or it may result 

 from fermentation or decomposition. Either of the substances named 

 will form a deposit on standing. 



When such a deposit is to be examined, a few ounces of the urine 

 should be set aside for several hours in a tall, narrow, cylindrical 



