1911.] Serum Reactions in Pulmonary Tuberculosis. 383 



of storage. Loss of fixation strength in sera containing sensitiser has been 

 observed to take place within a few clays, while storage of inhibitive sera 

 usually causes a less rapid loss of activity. Four inhibitive sera, sealed and 

 frozen in pairs on November 16, 1910, and November 26, 1910, were tested 

 on December 12, 1910. One serum of each date showed full activity, the 

 other two but slight loss. 



(7) Serum Suspension. — Bordet and Gay have shown that the inhibiting 

 effect of normal rabbit serum in specific haemolysis " is not clue to any effect 

 upon the sensitisation of corpuscles nor to any neutralising action upon 

 complement, but that the addition does oppose the fixation of complement 

 by the sensitised cells." Further, as has been shown, this retarding or 

 hindrance of the specific reaction is offset by increasing the avidity of the 

 antigen-amboceptor for complement, or by dilution with salt. This effect of 

 inert serum in contrast to salt solution as a medium can appropriately 

 be described as serum suspension, and it seems logical to conclude that serum 

 provides unfavourable physical conditions in contrast to salt solution as a 

 suspending medium. Accepting this explanation of the suspension effect of 

 serum, one may suppose that the presence of any serum may tend under favour- 

 able circumstances to the end-result of lessened haemolysis. Certain results 

 strongly support this conception. 



With some inhibitive sera irregularities in the end result with increasing 

 amounts of serum seem explicable on this ground. Thus when O'l c.c. serum 

 gives as complete an inhibitive reaction as - 3 c.c. serum, the end result of 

 the latter can sometimes be increased by further saline dilution. The 

 technique can easily be modified by using more closely related amounts of 

 ■anti-complementary strengths so that the degree of the inhibitive reaction 

 can be more closely read. In other words, saline dilution encourages specific 

 reaction by off-setting the suspending effect of larger amounts of serum. The 

 anti-complementary effect of antigen can be lessened by saline dilution as 

 well as by increase of the avidity of corpuseles-haemolysin, so that to some 

 extent the absence of haemolysis under this condition seems to be due to a 

 suspending effect of antigen upon complement. These effects are partially 

 shown in Table VI, by Serum 1354, which had previously given the same 

 result with 0-2 c.c. as with 03 c.c. quantities. 



Serum suspension may thus under favourable conditions tend to simulate 

 specific fixation. This makes it essential for one to know in each protocol as 

 accurately as possible how much prevention of haemolysis serum itself may 

 cause, and, as has been pointed out in the remarks under antigen saline 

 control, how much prevention of haemolysis by the fourth dilution of antigen 

 before one can feel certain to what extent the combined antigen-serum tube 



