124 CLINICAL BACTERIOLOGY AND H^EMATOLOGY 



been introduced we shall describe two, which are not beyond 

 the power of an enthusiastic practitioner to repeat, and which 

 give excellent results. 



\ 

 AUTHOR'S MODIFICATION OF THE WASSERMANN REACTION. 



Collection of Blood. The specimen to be examined should 

 be collected in a Wright's curved pipette in the manner 

 already described. A fair-sized sample (10 to 20 drops) is 

 advisable. If an incubator is at hand, it is a good plan to 

 incubate the specimen for half an hour or so to insure quick 

 coagulation and a good retraction of the clot, as by this 

 means a large crop of serum is secured. Then centrifugalixe 

 a short time to throw down the clot and insure clear serum. 



i. Preparation of the Antigen. Take a sheep's heart, 

 cut out a piece of muscle, free from fat and connective 

 tissue, and weigh it. For each gramme of muscle take 

 9 c.c. of absolute alcohol. Mince the meat fine, grind it in a 

 mortar with some clean, dry sand or fragments of glass, add 

 the alcohol, continue the grinding for a few minutes, bottle 

 off, and shake occasionally for two or three days. Do not 

 filter, but decant the clear supernatant fluid for use. 

 Prepare also a i per cent, solution of pure cholesterin 

 in absolute alcohol, applying gentle heat. For use, mix 5 

 parts of heart extract with 4 of cholesterin. The two 

 fluids keep best separately, but the mixture will keep for 

 some weeks. To dilute it, take the requisite amount of 

 normal saline, measure out the mixed fluid in a pipette, and 

 mix as quickly as possible (as recommended by Mclntosh 

 and Fildes). 



In most cases this may be used at a dilution of i in 10 of 

 saline, but it is advisable to standardize it from time to time, 

 the strength aimed at being- that which just causes slight 

 inhibition of haemolysis under standard conditions with nor- 

 mal serum. Proceed as follows. Take as many samples as 

 convenient of fresh normal (non-syphilitic) serum, and pre- 

 pare a dilution of antigen i in 10. Put up a mixture of i part 

 of serum and 4 of antigen, using a pipette, as described sub- 

 sequently, and incubate five minutes. Then add i part of 

 20 per cent, emulsion of red corpuscles and i part of ambo- 

 ceptor, taking each separately in the pipette, separated by a 

 bubble of air, so that they do not mix until they are in con- 



