208 INFECTION AND RESISTANCE 



serum phenomena is worse than useless in that insufficient attention 

 to special conditions and to details may easily result in a positive re- 

 action when syphilis is not present, and vice versa. 



Recently Archibald McNeil and others have exposed the mix- 

 tures of complement, antigen, and patients' serum at refrigerator 

 temperature for a number of hours instead of in the water bath or 

 thermostat at 37.5 C., before adding the sensitized cells. It is a 

 curious fact, which has not yet been satisfactorily explained, that 

 such a procedure increases the delicacy of the reaction. It may be 

 that, when the tubes containing the antigen, patient's serum, and 

 alexin are left at incubator temperature, partial alexin fixation only 

 can take place during the brief period of 30 minutes to one hour, 

 which is usually employed. More prolonged exposure at this tempera- 

 ture would not be advisable on account of deterioration of the alexin. 

 On the other hand, at ordinary ice-box temperatures of about 8 to 

 10 C., the exposure can be continued for as long as 10 hours without 

 extensive complement deterioration, and meanwhile more complete 

 fixation can occur. This, however, is a surmise. The actual condi- 

 tions are not clear. As a matter of fact in our laboratory Dr. Otten- 

 berg, in 120 cases so far done in parallel series, one being exposed 

 for fixation for 30 minutes at 37.5 C., the other at 8 to 10 C. for 

 three hours, found discrepancies between the two methods in 15 

 cases. In all of these, positive reactions were obtained by the ice-box 

 method, whereas by the water bath method the results were negative. 

 Of these cases 7 were clearly unquestionable syphilitics, two were 

 treated syphilis, and four were probably syphilitic. 



Many modifications of the Wassermann test have been suggested. 

 Probably the most important is that of Noguchi. The chief justifi- 

 cation for this modification is the fact that many normal human sera 

 contain hemolysins for sheep corpuscles. For this reason many 

 workers carry out the ordinary Wassermann technique without add- 

 ing antisheep sensitizer or amboceptor until they have first observed 

 whether or not the tested serum (in the "back row," without antigen) 

 will not hemolyze the corpuscles without such an addition, adding 

 the sensitizer only when this does not take place. This is advisable 

 since the presence of any considerable amount of normal antisheep 

 sensitizer in the human serum which is being examined (if added to 

 the amount used in the ordinary reaction, 2 units), may so increase 

 the total quantity that hemolysis will result even after most of the 

 alexin has been fixed. Noguchi excludes this uncertainty by avoid- 

 ing the use of the "sheep cell-antisheep sensitizer" system entirely, 

 substituting a hemolytie complex consisting of human cells and anti- 

 human sensitizer, produced by injecting washed human corpuscles 

 into rabbits. 



His technique may be best illustrated in the following tabula- 

 tion: 



