Abstract
The proposed method possesses the following three advantages over the Meinicke, 1 Sachs and Georgi, 2 and Dreyer and Ward 3 (Sigma) precipitation reactions.
1. The diluted antigen possesses considerable stability, rendering it unnecessary to dilute fresh antigen before using in the tests.
2. The strongly positive serums show, in most cases, spontaneous precipitation and the test as a whole is completed after 3 hours incubation in the water bath.
3. The precipitates can be easily distinguished with the naked eye.
The Method.—The antigen is prepared according to Neumann and Gager. 4 After extracting the dried heart muscle with ether and drying as indicated by these authors, 5 c.c. of absolute alcohol is added to each gram of material.
The alcoholic extraction is carried on for about 10 days in the ice box. It is then filtered and fresh alcohol added to the extent of the amount filtered off. The second extraction is carried out for about a month in the ice box. Both filtrates may be used as antigens.
Add rapidly three parts of salt solution to I part of antigen. The mixture should be opalescent and but slightly milky. No precipitate should form after standing over night at room temperature. Antigens conforming with these requirements have been kept for 2 weeks without any apparent change in an tigenic properties.
Add 0.1 c.c. of antigen to 0.3 C.C. of clear inactivated serum and incubate in the water bath. The strongly positive sera show immediate clouding and, withir 5 min., visible precipitation. For uniformity, the tests are read after 1 hour and 3 hours incubation. Those showing marked precipitation at the end of 1 hour are considered strongly positive; marked precipitation at the end of 3 hours are considered positive; weak precipitation, weak positive and questionable, doubtful positive.
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