BUREAU OF ANIMAL INDUSTRY. 



635 



indicate that the seventh tube had been inoculated from the sixth, 

 and that the original culture from the spleen of the animal was not 

 more than seven or eight days older than the seventh. 



In the following experiment two pigeons received two injections 

 of heated cultures, two received injections of cultures which had 

 been evaporated on a water bath to one-half or one-third the original 

 volume and restored to this volume by the addition of sterile dis- 

 tilled water, and two were reserved as checks. The cultures used 

 were from eighteen to twenty-three days old. All received those in- 

 jections beneath the skin of the right pectoral. Five days after the 

 second inoculation each received beneath the skin of the left pecto- 

 ral I''" of the ordinary unattenuated culture. On the following day 

 one of the check pigeons was dead and one sick, as shown by the 

 ruffled plumage and quiet position. Those which had received the 

 heated culture were both well and remained so. Of the two which 

 had received the evaporated culture one was well, and the other sick, 

 which died two days later. From the blood from the heart a pure 

 culture of the bacterium of hog-cholera was obtained. A few bac- 

 teria were found in cover-glass preparations of the liver and blood. 

 The dead muscular tissue of the pectoral was already beginning to 

 separate as a sequestrum. 



This experiment seemed to point to a partial destruction of the 

 element producing immunity during the process of evaporation. 



A number of other experiments were made, which are tabulated 

 below. In some the culture liquid was evaporated on the water bath 

 to dryness and again diluted in sterile water. In others the culture 

 liquid was simply heated to 58° C. to devitalize it. This was tested, 

 as before, in every case by inoculating sterile infusions therefrom. 

 In a few experiments the age of the culture was limited to three 

 days. 



The results of these experiments show that evaporated cultures 

 are less efficacious than heated ones; also that a single injection is 

 not protective. A period of two days between consecutive inocula- 

 tions seems to be sufficient to protect. It will be observed that the 

 experiments were most uniformly successful in the -winter. As the 

 warm weather approached the birds became less susceptible, so that 

 the checks failed to take the disease in some experiments. In the 

 mnter they usually died within twenty-four hours after inoculation 

 with strong virus. Grains of corn in the beak and oesophagus indi- 

 cated partial regurgitation of food from the crop. Later on the birds 



