THE RELATION OF LIPOIDS TO IMMUNITY 



565 



All tubes should be carefully labeled, their drop numbers determined, 

 and then placed in an incubator at 37 C. for two hours or in the water- 

 bath at 50 C. for one hour. At the end of this time they are removed, 

 allowed to cool, and the drop number of each is determined. 



The controls are first examined to show that the antigen has not 

 undergone any change. Variations of the number above one and a half 

 or two drops (as compared with the control containing distilled water in- 

 stead of antigen) .are regarded as positive reactions. The increase in drops 

 is seldom greater than eight. 



TABLE 21. MIOSTAGMIN REACTION IN CANCER 



Other Methods for Preparing Antigens. Various methods for pre- 

 paring antigen and conducting the test are to be found in the literature, 

 and it is extremely difficult to arrive at a correct conclusion as to which 

 is the best method for preparing antigen. Among these methods for 

 the preparation of antigen other than those previously described are 

 the following: 



1. After securing the alcoholic extract described elsewhere evaporate 

 it to dryness. Again extract in methyl alcohol and evaporate. Extract 

 with warm ether, renewed several times during the course of twenty- 

 four hours. Dry, and repeat the extraction several times until the 

 alcohol remains colorless. Evaporate the alcoholic and ethereal ex- 

 tracts at 50 and 37 C. respectively. A yellowish-red, sticky mass 

 results. Dissolve this in a large amount of water-free ether. Filter, 

 and evaporate at room temperature until a slight powdery precipitate 

 is deposited. This solution constitutes the stock antigen, which, how- 

 ever, may require still further concentration. 



2. A synthetic cancer antigen may be prepared by grinding up 0.5 

 gram of lecithin (ovolecithin Merck, or lecithin Richter), and extract it 

 with 50 c.c. of acetone for twenty-four hours at 50 C. Filter through 

 Scheicher and Schull's filter-paper No. 590, until clear. Just before 



