556 THE RELATION OF COLLOIDS AND LIPOIDS TO IMMUNITY 



It was now possible, according to Lange, to measure the protein 

 content of spinal fluid according to the degree of precipitation, and very 

 interesting and practical results have been secured, although it cannot 

 be stated as proved that the precipitation is due entirely to protein, 

 particularly since it has been shown that the globulins may actually 

 protect colloidal gold against precipitation. Zaloziecki 1 regards the 

 reaction as a form of immunity reaction; Jaeger and Goldstein 2 consider 

 it purely physical and probably of an electric nature. 



Preparation of Colloidal Gold. The preparation of colloidal gold 

 is frequently an exceedingly troublesome procedure, and the success 

 of the test depends upon a satisfactory preparation. The method which 

 I shall briefly describe here is after that of Miller, Brush, Hammers, 

 and Felton, 3 which I have found to yield fairly constant and satisfac- 

 tory products. 



The glass-ware (beakers, pipets, and test-tubes) must be absolutely dean. 

 They may be washed in hot water with ivory soap; rinsed in tap-water 

 for five minutes; placed in hot bichromate cleaner for half an hour; 

 rinsed in tap-, and finally triple distilled water. The beakers should be 

 used at once; the pipets and test-tubes are to be dried in a hot-air oven. 

 Thermometers should be cleansed in a similar manner. 



It is necessary to use water triply distilled in an apparatus free of 

 rubber connections. The reagents should be freshly prepared of the best 

 products obtainable. 



1. Heat 1000 c.c. of triply distilled water over a good Bunsen burner 

 in a prepared beaker with a thermometer. 



2. At 60 C. add 10 c.c. of a 1 per cent, solution of Merck's gold 

 chlorid c^stals in triply distilled water and 7 c.c. of a 2 per cent, solu- 

 tion of Merck's blue label potassium carbonate in triply distilled water. 



3. At 80 C., while stirring briskly, add 10 drops of a 1 per cent, solu- 

 tion of Merck's blue label oxalic acid crystals in triply distilled water. 



4. At 90 C. remove the burner and, while stirring, add 5 c.c. of a 

 solution of 1 c.c. of Merck's highest purity formaldehyd in 40 c.c. of 

 triply distilled water, or enough to produce an initial pink color. 



5. The solution must be neutral in reaction when used, and for this 

 purpose is tested with a 1 per cent, solution of alizarin red in 50 per cent, 

 alcohol. With this indicator the neutral point is a brownish-red tint; 

 an acid solution gives a lemon-yellow, and an alkaline solution a pur- 

 plish-red, color. 



1 Deutsch. ztsch. f. Nervenhl., 1913, xlvii, 783. 



2 Ztsch. f. d. ges. Neur. u. Psych., 1913, xvi, 219. 



3 Bull. Johns Hopkins Hosp., 1915, xxvi, 391. 



