32 



BIOLOGICAL SOCIETY OF WASHINGTON. 



February 13, one week after the last injection, these birds were 

 inoculated with strong virus, the quantity injected being .7=5 cc. 

 which had hitherto proved invariably fatal, with the single excep- 

 tion of the bird that had been previously treated with heated virus. 

 Those inoculated were Nos. 10, 11, 12, 13, which had received 

 the heated virus, also No. 14, the check pigeon, which had not 

 been touched, and No. 8, which had received a small quantity, 

 .8 cc. of heated virus, December 24, over 50 days before. 



On the following day the check pigeon (No. 14) was found 

 dead ; the one which had received the smaller dose (No. 8) was 

 very ill and died before the next day. The other pigeons were 

 perfectly well. The effect of this dose of strong virus, so re- 

 markable on the unprotected pigeons, was even more evanescent 

 than that of the heated virus in which all life had been destroyed. 



There can be no doubt, therefore, from this very positive 

 result, that the pigeons had acquired an immunity through the effect 

 upon the tissues of the chemical products formed by the bacterium 

 in the culture liquid. 



A table giving the dates of the injections and the quantity intro- 

 duced into each animal is given below : 



In the birds that died, (Nos. 8 and 14), the pectoral muscles at 

 the place of injection were pale and friable. Necrosis was 



