932 THE AMERICAN NATURALIST. 
five to six months. The pleuritic fluid had been preserved in 
a corked bottle with chloroform. These observations seem to 
me to possess a particular interest. 
It seemed of interest, from a medico-legal standpoint, to 
determine whether or no a mzxture of several kinds of blood 
would prevent the detection of one of the bloods in the mix- 
ture; the presence of another blood might inhibit the action 
of the anti-serum. To determine this question 1: 100 dilutions 
of two to six kinds of blood were mixed together in equal pro- 
portions and tested with positive results. 
CONCLUSIONS. 
1. The investigations we have made confirm and extend the 
observations of others with regard to the formation of specific 
precipitins in the blood serum of animals treated with various 
sera. 
2. These precipitins are specific, although they may produce 
a slight reaction with the sera of allied animals. 
3. The substance in serum which brings about the forma- 
tion of a precipitin, as also the precipitin itself, are remarkably 
stable. 
4. The new test can be successfully applied to a blood which 
has been mixed with that of several animals. 
5. We have in this test the most delicate means hitherto 
discovered of detecting and differentiating bloods, and conse- 
quently we may hope that it will be put to forensic use. 
UNIVERSITY OF CAMBRIDGE, 
CAMBRIDGE, ENGLAND. 
