296 Wassermann Reaction for Diagnosis of Syphilis 



tity removed as needed. The most convenient way of treating it 

 seems to be Noguchi's method of drying it upon filter-paper. 



For this purpose a good quality of filter-paper is cut into strips 

 10 to 20 cm. in length and 6 to 8 cm. in breadth, and saturated with 

 the serum, which is permitted to dry. It is well to make a pre- 

 liminary titration of the serum, for if it be very active it may have 

 to be diluted in order that the piece of dry paper containing the dose 

 be of a size convenient to handle; i drop of serum usually covers 

 about J^ sq. cm., which is about as small a piece as can be measured, 

 cut, and used with satisfaction if sufficient allowances are to be 

 made for variations in distribution and other conditions that may 

 modify the accuracy of the method. If the unit-strength of a serum 

 be, say, 0.00005 ^.nd the dose o.oooi, water should be added to the 

 extent of about 9 volumes and the mixture gently agitated, so that 

 diffusion may occur without frothing. The diluted serum is poured 

 into a large flat dish, and the strips of paper passed lengthwise and 

 slowly to and fro until not only wet, but thoroughly saturated, 

 each strip, when the dipping is finished, is held first by one end, 

 then by the other, to drain off the free drops, and then laid flat 

 upon a clean glass plate and permitted to dry. The use of an electric 

 fan is recommended to hasten drying. Paper so prepared contains 

 ieverywhere about the same quantity of serum. 



The real titration o£ the serum now begins. With a ruler, one piece of paper 

 is divided into squares of, say, J^ cm., and a series of tubes prepared with cor- 

 puscle suspension and complement and the paper added i square, 2 squares, 

 2}4 squares, and so on until the unit is determined. When that is achieved, 

 the exact size of the paper containing the unit being known, one sheet of the 

 paper can be ruled into squares of that size or into squares of twice that size — 

 since the "dose" is two units — at the option of the investigator. 



The sheets of paper should be kept tightly closed in a dry, glass- 

 stoppered bottle or jar, the quantity for each test being cut off as 

 needed. The dry serum changes sp httle that the dose once deter- 

 mined, the size of the square of paper needed for the test remains 

 about the same. 



The method has the advantage that the amboceptor serum can- 

 not be spoiled or spilled. It has the disadvantage of being sUghtly 

 less accurate, though it must be admitted that the chances of error 

 in measuring and diluting the fluid serum are probably as great 

 as those arising from inequahties in the distribution of the seirum 

 throughout the paper. 



(4) The Antigen. — It has already been shown that complement 

 is labile, and it may have occurred to the reader that its activity 

 is similar to that of ferments. It is now necessary to point out the 

 many conditions (some of which may arise in the performance of 

 a test so delicate as the Wassermann reaction) by which the comple- 

 mentary action may be affected or set aside. Thus, temperature 

 affects it, and temperatures of o°C. suspend it. It is on this ac- 

 count that the test is always made at 37°C. Like most of the 



