SERUM DIAGNOSIS OF SYPHILIS. 169 



From a practical standpoint, however, no distinct advantage is offered by these 

 modifications. In fact, it is the claim of Wassermann and his pupils that by the use of 

 human blood, the error tends towards the opposite direction, i.e., the percentage of posi- 

 tive results obtained are higher than is actually the case. 



The number of modifications have become so numerous that almost 

 every one employs his own "method." There is absolutely no necessity for 

 this, as an innovation justifies its existence only if it is a distinct improve- 

 ment, i.e., discloses a new fact or radically simplifies the old. 



It is the classical Wassermann reaction performed in the original manner 

 which has taught physicians how valuable a clinical aid it is. Their knowl- 

 edge has not advanced a step further even with all the new changes. A 

 single advantage only has been instituted through all this agitation, and that 

 was the discovery that the luetic antigen can be replaced by the alcoholic 

 extract of guinea-pig's heart. In important differential diagnosis, however, even 

 this kind of extract should not be considered as specific as luetic liver antigen. 



For general work, however, its employment may be of service. 



The antigen of Landsteiner, Muller and Potzl is prepared as follows: 



The heart of a guinea-pig is washed free of blood, its muscular part finely divided 

 or macerated in a mortar and then extracted with 95 per cent, of alcohol for several 

 hours at 60 C. One gram of the heart substance should be mixed with 5 c.c. of the 

 alcohol. The material is then passed through filter-paper, the filtrate being kept at 

 room temperature. [The editor prepares the alcoholic extract by simply placing the 

 finely divided guinea-pigs' hearts into 95 per cent, alcohol and allowing them to remain 

 there for almost four weeks for purposes of extraction. At the end of this period the 

 alcoholic solution is titrated and can be employed as antigen.] 



These authors also employ the so-called drop method: 

 Drop Ten drops of saline and i drop of normal guinea-pig's serum as 



Method. complement is placed into each test-tube. The individual tubes then 

 receive the following ingredients: 



First tube: One drop of the inactivated serum for examination. 



Second tube: Same as one -I- 2 drops of the alcoholic heart extract. 



Third tube: One drop of inactivated, surely luetic serum. 



Fourth tube: Same as three + 2 drops of alcoholic heart extract. 



Fifth tube: One drop of inactive normal serum. 



Sixth tube: Same as five + 2 drops of alcoholic heart extract. 



Seventh tube: Two drops of extract. 



The tubes are well shaken and placed into the incubator for one hour at 

 37 C. Then i drop of a 50 per cent. (!) suspension of washed sheep's 

 erythrocytes and i drop of hemolysin (double the maximum hemolytic 

 titer) are added. After one-half hour in the incubator, the results are read 

 off. 



Bauer entirely excludes the immune hemolysin. His reaction requires 

 Bauer's the following ingredients: 

 Modification, i. Fresh guinea-pig's complement. 

 2. Alcoholic organ extract. 



