322 PRECIPITINS 



serums are capable of producing flocculent precipitates from solutions 

 of lecithin and similar salts. Two-tenths of a cubic centimeter of a 1 

 per cent, solution of Merck's sodium glycocholate in distilled water is 

 placed in narrow test-tubes, and an equal amount of the patient's 

 serum, which must be absolutely clear and inactivated by heating at 

 56 C. for thirty minutes, is added. This mixture and the known nor- 

 mal and luetic controls are kept at room temperature for from eighteen 

 to twenty-four hours. A positive reaction is marked by the appearance 

 of distinct coarse flocculi, mere turbidity or faint precipitation being 

 regarded as negative. 



Herman-Perutz Reaction. More recently Herman and Perutz have 

 devised a similar test requiring the following two solutions : Solution 1 

 (stock solution, diluted 1 : 20 with distilled water before use) consists of: 

 Sodium glycocholate, 2 gm., cholesterol, 0.4 gm.; 95 per cent, alcohol, 

 100 c.c. Solution 2 (freshly prepared before use) is a 2 per cent, solu- 

 tion of sodium glycocholate in distilled water. The test is performed by 

 adding to 0.4 c.c. of clear inactive serum (heated at 56 C. for half an 

 hour) in a small test-tube 0.2 c.c. of solution 1 and 0.2 c.c. of solution 2. 

 The tubes are tightly plugged with cotton and set aside at room tem- 

 perature for twenty-four hours, after which the presence or absence of 

 precipitation is noted. It is well in this test, as in all immunologic re- 

 actions, to prepare controls with known normal and luetic serums and 

 with distilled water. 



None of these reactions has been found specific, and none has been 

 generally adopted, the far greater accuracy of the Wassermann reaction 

 having made this method more valuable. 



Noguchi Butyric-acid Test. Noguchi has devised a very useful 

 test for the detection of an increased amount of protein, particularly 

 globulin, in cerebrospinal and other body-fluids. In my experience this 

 test has proved of particular value in establishing the differential diag- 

 nosis between serous and tuberculous meningitis, being negative in the 

 former and positive in the latter, whereas in both the fluid may be clear, 

 the cytology may be indefinite, and tubercle bacilli may escape detection. 

 Serous meningitis is not a true infection, but a reflex vasomotor disturb- 

 ance of the cerebral vessels, causing an outpouring of serum that leads 

 to various pressure symptoms closely resembling those of a true meningi- 

 tis. This condition is particularly common during childhood, and the 

 general symptoms, the increased pressure of the cerebrospinal fluid, and 

 its clear, watery character, are features that resemble those of tubercu- 

 lous meningitis. It is just in such cases and they are frequent that 

 I have found this protein reaction of considerable value. A positive 



