176 STRONG AND TEAGUE. 



lining the alveoli appear normal even when they contain large 

 numbers of bacilli. Although the blood vessels between the 

 lobules and septa were dilated, and hsemorrhages sometimes 

 occurred, practically no bacteria were found within them. 



From these observations, it is obvious that the infection in 

 monkeys occurred by inhalation and resulted in primary plague 

 pneumonia. 



It also is evident that in some instances in which monkeys 

 are exposed to infection by inhalation, the primary point of 

 infection may be not only the lungs, but also the mucous mem- 

 branes of the mouth and throat. That plague infection may 

 occur through the mucous membranes of the mouth and throat 

 alone in monkeys was demonstrated by placing a small quantity 

 of plague bacilli upon the posterior portion of the throat by 

 means of a glass rod. The following experiments are given as 

 examples of such infection. 



EXPERIMENT I. 



Monkeys Nos. 5882, 5883, and 5884 were all infected in the following 

 manner on November 7. 



A necropsy was performed upon monkey No. 5876 which had just died 

 of experimental pneumonic plague and a portion of the pneumonic lung was 

 cut into small pieces in a Petri dish. A glass rod with the end rounded 

 in a flame was dipped into the oedematous fluid in the Petri dish and passed 

 over the tongue and rubbed against the pharynx of each of the three monkeys 

 (Nos. 5882, 5883, 5884). The monkeys held their tongues so that the glass 

 rod was squeezed between the soft palate and the tongue and most of the 

 material on the rod was evidently caught there. All three of the monkeys 

 were treated in the same way and then the rod was dipped into the same 

 fluid and touched to the shaved skin of a guinea pig as a control. The 

 control guinea pig, No. 5885, died November 14, seven days after, with 

 typical lesions of plague. 



Monkey No. 5882 was found dead on Nov. 13, six days after infection. 

 Necropsy: The superficial cervical glands are swollen on both sides. Both 

 submaxillary glands are swollen and haemorrhagic. The changes are more 

 marked on the left side. The deep cervical glands on both sides are also 

 swollen and haemorrhagic ; the process is more advanced on the left side. 

 The axillary lymph nodes are also swollen and haemorrhagic. The lesions 

 in these glands are more marked on the right side. The tonsils on both sides 

 are swollen and reddened. The larynx shows slight injection. The trachea 

 contains a small amount of pale, frothy fluid; its mucosa is not injected. 

 The bronchial lymph nodes at the bifurcation of the trachea are very small. 

 There is no evidence of pneumonia in either lung. The spleen is much 

 swollen and very soft. Smears from the spleen and blood show innumerable 

 plague bacilli. Smears from the cervical and axillary glands show very 

 numerous plague bacilli. Smears from the lung show fair numbers of 

 plague bacilli. Sections of the tonsils show no evidence of primary plague 

 infection and but few bacilli. 



