SUSCEPTIBILITY OF ANIMALS. 227 



unable to infect the donkeys, even when they were made to in- 

 hale air charged with the most virulent cultures of pneumonic 

 strains of the plague bacillus for a period of as long as five 

 minutes at a time. We, therefore, do not consider donkeys 

 susceptible to pneumonic-plague infection, and these experiments 

 render it doubtful that these animals played any part in the dis- 

 semination of pneumonic plague during the Manchurian epide- 

 mic, and suggest that in the reported cases of pneumonic plague 

 in donkeys the infecting organism was not Bacillus pestis, but, 

 perhaps, some other organism of the hsemorrhagic septicaemia 

 group. 



DOGS. 



At the Mukden Conference," 1 case of pneumonic-plague in- 

 fection in a dog, observed by Doctor Takami, was referred to 

 in which there was pneumonia in the caudal lobe of the left 

 lung. This dog was found in a house where 7 people had died 

 of plague infection. The Conference also resolved that the ques- 

 tion of the occurrence of pneumonic plague in dogs should be 

 made the subject of special study with regard to their liability 

 to this infection. Accordingly, we also performed experiments 

 with this object in view. The results were as follows: 



On November 4, 2 fully grown dogs were placed in a closed 

 glass cage and a suspension of two 48-hour agar-cultures of a vir- 

 ulent pneumonic strain of the plague bacillus was sprayed into 

 the cage for tw^o periods of two and one-half minutes, each after 

 a brief interval between them. The first dog. No. 5880, died 

 on November 9, five days after infection. The necropsy show^ed 

 there was pneumonia of both lungs. In the right lung all the 

 lobes were involved. Only a small portion at the apex of the 

 upper lobe did not show pneumonia. In the left lung, both 

 lobes, with the exception of the apex of the upper lobe, were 

 also involved. The pneumonia was in the stage of engorgement 

 with the exception of small bronchial areas scattered throughout 

 the lung, measuring from about 2 millimeters to 1 centimeter 

 in diameter. These areas of bronchial pneumonia were grayish 

 in color on the surface of the lung, and on section they were 

 grayish at the periphery and in the center red and slightly gran- 

 ular. The areas were not wedge-shaped, but were circular in 

 outline (see Plate XII, fig. 1). Smears from the lungs showed 

 comparatively few plague bacilli and a few streptococci. The 

 large bronchi were not reddened. There was much mucus in the 



" Loc. cit. 



