446 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



sensitive antigens. In other words, one should use every precaution and 

 exercise great care before making a diagnosis; when lues is known to be 

 present, however, the treatment should be thorough, and there would seem to 

 be no better criterion for judging the state of the infection than repeated 

 negative reactions with cholesterin extracts. 



Preparation. These extracts are prepared of human, ox, and guinea-pig heart. 

 Human heart usually yields the best extract. Care should be taken to use only 

 muscle and to avoid fat. To 10 grams of minced muscle add 100 c.c. of absolute 

 ethyl alcohol. Shake in a mechanical shaker for twenty-four hours, and continue 

 the extraction in the incubator for ten days or two weeks. Then filter through fat- 

 free filter-paper, and add absolute alcohol to make up for the loss through evapora- 

 tion. Add 0.4 gram of Kahlbaum's cholesterin (0.4 per cent.); shake well and stand 

 aside in the refrigerator for a few days. The cholesterin goes into solution slowly in 

 cold alcohol, and 0.4 per cent, of cholesterin usually saturates the solution. After 

 a week the extract may be again filtered and stored in a tightly stoppered bottle. The 

 slight sediment that may form should not be disturbed. 



These extracts keep fairly well. Different preparations are quite 

 similar in their properties; they are usually found to be highly antigenic 

 and no more anticomplementary than crude alcoholic extracts. They 

 constitute, therefore, inexpensive and very sensitive antigens. 



5. Acetone-insoluble Lipoids. As previously stated, crude alco- 

 holic extracts may contain an excess of undesirable constituents, such 

 as neutral fats, fatty acids, soaps, and certain protein materials, which 

 are responsible for the untoward anticomplementary and hemolytic 

 effects. To eliminate these Noguchi advised the exclusive use of the 

 acetone-insoluble fraction instead of the entire unfractionated alcoholic 

 extract, especially if unheated human serums are used in conducting the 

 syphilis reaction. These extracts are composed essentially of lecithins, 

 which, when prepared from any one source, consist of a mixture of 

 analogous bodies; lecithins from different sources vary in their compo- 

 sition. In speaking of lecithins, one is prone to regard them as chemicals, 

 and to overlook their biologic properties. Noguchi no longer employs the 

 term lecithin to designate the acetone-insoluble fraction of tissue lipoids. 



These antigens are readily prepared of ox-heart or of human liver, 

 the former being preferable for use. Their main disadvantage is the 

 expense of preparation, for it may be necessary to prepare several 

 extracts before one that is satisfactory is secured. A good extract will, 

 however, keep well, and is a reliable and valuable antigen for the testing 

 for the syphilitic reaction. 



Preparation. A mashed paste of the muscle of ox-heart is extracted with 10 

 parts of absolute alcohol at 37 C. for four days. It is then filtered through filter- 

 paper and the filtrate collected and brought to a state of dryness by evaporation. 

 The use of the electric fan is not necessary, for if poured into large flat dishes, the 

 filtrate will evaporate in from twelve to twenty-four hours. The residue is then 

 taken up with a sufficient quantity of ether, and the turbid ethereal solution is allowed 



