No. 419-] SPECIFIC ANTI-BODIES IN THE BLOOD. 931 
The tests made with dried blood, whether dried on glass 
or filter-paper, gave perfect reactions, as did also 1:100 
dilutions kept for two weeks in test-tubes in the laboratory. 
Although chloroform had been dropped into the bottom of 
these tubes, molds occasionally developed upon the surface of 
the serum; but this seemed in no way to interfere with the 
specific reaction. Strips of filter-paper upon which both sheep 
and ox blood had been allowed to dry were placed under dif- 
ferent conditions. Some were kept for two months at 37° C. 
in the dark; others at room temperature in the dark, and in 
diffused light for the same period ; others again were exposed 
for éight days to the action of sunlight in a window. All of 
these samples gave apparently just as good reactions as fresh 
bloods, though of course our method cannot as yet be strictly 
considered to be quantitative. The body in the serum which 
is acted upon by the anti-serum, and the specific body in 
anti-serum, seem to be about equally resistant. Anti-serum 
dried for forty-two days on filter-paper and then dissolved 
in salt solution was found to give a perfectly characteristic 
reaction when added to its homologous (ox) serum, the 
latter diluted (1:100) as usual; it did not, however, produce 
a reaction in dilutions of other bloods. Dried normal sera 
exposed for half an hour to a temperature of 100? C. still gave 
à clear reaction, as did also 1:100 dilutions exposed for half 
an hour to'55?. As I first showed, the bactericidal properties 
of blood are destroyed at the latter temperature. Dilutions of 
blood exposed to a temperature of 100? gave no reaction. ; 
The first rabbit in the series treated by horse-serum injections 
received old anti-toxic serum which had been kept at room tem- 
perature in the laboratory for two years and seven months, We 
are indebted to Dr. Louis Cobbett for this serum. The serum, 
to which trikresol had been added, had been kept in a corked 
bottle, exposed to diffused light, the temperature of the room 
being very high during the summer months. The first and , 
second rabbits of the series treated with human pleuritic €xu- 
dation, etc., received only one and two injections respectively 
of fresh serum, being treated for the rest of the time with 
pleuritic effusion which had been kept at room temperature for 
