THE RELATION OF LIPOIDS TO IMMUNITY 527 



drops found in a cubic centimeter determined with a specially devised 

 instrument known as Traube's stalagmometer. The antigen is so diluted 

 that when mixed with this normal serum it does not increase the number 

 of drops more than one in a cubic centimeter. When properly diluted 

 patient's serum and antigen are mixed, it may be found that the number 

 of drops is increased from 2 to 8 in a cubic centimeter. This constitutes a 

 positive reaction. The reaction is apparently due to the lowering of sur- 

 face tension, so that more and smaller drops are found; hence the term 

 "miostagmin'' has been applied to the test, the word being devised from 

 the Greek, meaning "small drop." 



The reaction is said to be sharply specific and very delicate, so that 

 antigens diluted up to 1 : 100,000,000 or higher may be detected. The 

 technic requires considerable practice and experience or erroneous 

 results are quite likely to occur. 



The exact nature of the reaction is not known. The antigens are 

 soluble in alcohol, but their nature is obscure. The antibody involved 

 in the reaction is referred to as the miostagmin, but its relation to other 

 antibodies is also unknown. It is probably a physicochemical or col- 

 loidal reaction, and for this reason it has been placed in this chapter. 



Technic. The antigen is most difficult to prepare. A recent method 

 described by Ascoli is as follows: 



1. Cut non-degenerated portions of malignant tumor (cancer or 

 sarcoma) into small pieces and dry in vacuo or spread out in a thin 

 layer on clean glass plates and keep at a temperature of 37 C. 



2. Pulverize the dried substance and extract with pure methyl 

 alcohol (in the proportion of 5 gm. to 25 c.c.) for twenty-four hours at 

 50 C. in closed vessels, and shake occasionally. 



3. Filter while still hot, and allow the nitrate to cool, and then filter 

 again through Schleicher and Schull's filter-paper No. 590. 



4. It is now necessary to titrate the antigen and to determine in what 

 dilution it should be employed. Various dilutions of the antigen are 

 made with distilled water, as, e. g., 1:10, 1 : 25, 1 : 50, 1 : 100, 1 : 150, 

 1 : 200, etc. A fresh normal serum is diluted 1 : 20 with normal salt 

 solution, and 9 c.c. of this are mixed with 1 c.c. of the various antigen 

 dilution. Into another tube place 9 c.c. of the diluted serum and 1 c.c. 

 of distilled water. All test-tubes, pipets, and other glassware used must 

 be perfectly dry. 



The tubes are gently shaken and placed in an incubator at 37 C. 

 for two hours. The drop number for each fluid is then estimated by 

 Traube's stalagmometer. This instrument is merely a finely and 



