226 STRONG AND TEAGUE. 



changes in the lungs were said to be similar to those seen in the 

 cases of human infection. In regard to the question of plague 

 infection in donkeys, the Conference resolved that the question 

 of the occurrence of pneumonic plague in these animals should 

 be made the subject of a special study with regard to their 

 liability to the infection. We, accordingly, have attempted to 

 infect donkeys experimentally with pneumonic plague by spray- 

 ing suspensions of virulent strains of pneumonic-plague bacilli 

 into a closed canvas bag, fastened about the donkey's head in 

 such a manner that it was necessary for the animal to inhale 

 the bacteria in breathing. The experiments were performed as 

 follows : 



Experiment 1. — September 16. Two 48-hour agar-slant-cultures of a 

 virulent pneumonic strain of the plague bacillus (isolated a few days 

 previously from monkey No. 5635, which died of pneumonic plague) were 

 suspended in saline solution and two-fifths of this suspension sprayed into 

 the sacks surrounding the head of each of 2 donkeys. One of the donkeys 

 coughed several times while the spraying was continued. The time of the 

 spraying occupied from three to four minutes. The remaining quantity 

 of the suspension of the agar-cultures, used in attempting to infect the 

 donkeys, was sprayed into a closed glass cage containing 6 guinea pigs, 

 and 5 loops of the same suspension were rubbed over the shaved abdomen 

 of another guinea pig. All of these guinea pigs died of plague infection, 

 the first six either of pneumonia or septicaemia with involvement of the 

 cervical glands and the seventh guinea pig of bubonic infection. Both of 

 the donkeys remained entirely healthy. 



Experiment 2. — September 29. One 48-hour agar-culture of a virulent 

 pneumonic strain of Bacillus pestis, isolated a few days before from 

 animal No. 5741, which died of plague infection, was suspended in about 

 10 cubic centimeters of salt solution and about two-thirds of this suspension 

 sprayed into both nostrils of a third donkey. The remainder of the sus- 

 pension of this culture was then sprayed into a closed glass cage, containing 

 6 control monkeys (Nos. 5771 to 5776). All of the monkeys died later 

 of pneumonic-plague infection. The third donkey remained healthy. 



Experiment 3. — October 7. A large pneumonic area of the left lower 

 lobe of a monkey that had just succumbed to pneumonic-plague infection 

 was cut into small pieces and crushed with a pair of forceps in salt solution 

 and the lung thoroughly broken to pieces. The suspension amounted in 

 volume to about 20 cubic centimeters. One-half of this suspension was 

 sprayed into a canvas sack surrounding the nostrils and head of one 

 donkey and nearly all of the other half into a second sack over the nostrils 

 and head of a second donkey. Guinea pig (No. 5802) was also inoculated 

 cutaneously with 5 oesen of this same suspension. The guinea pig died 

 three days later with typical bubonic-plague infection. The two donkeys 

 remained entirely healthy. 



Therefore, although we never failed to infect guinea pigs and 

 monkeys with pneumonic plague by the same cultures which 

 were sprayed into the nostrils of the donkeys, we were entirely 



