x,B,4 Crowell: Pathologic Anatomy of Bubonic Plague IR5 
changes of the lobular type, and shortly afterwards from the fusion of 
several rapidly spreading areas more general lobar involvement of the 
lung tissue * * *. The tonsils may become secondarily infected in 
pneumonic plague, just as other lymphatic glands—for example, the bron- 
chial ones—become so infected. However, in pneumonic plague death occurs 
before any very marked macroscopic changes occur in the tonsils. There is 
no doubt also that the tonsils may become primarily infected in epidemics 
of pneumonic plague, just as has occurred in sporadic cases during epidemics 
of bubonic plague. 
In many epidemics of primary bubonic plague sporadic cases 
of such primary respiratory infections occur and are probably 
to be explained by the same method of transmission as occurs 
in epidemics of primary pneumonic plague, the contagium in 
this case arising from the sputum of cases of primary bubonic 
plague with secondary pulmonary or pharyngeal lesions of the 
type about to be described. Teague and Barber *° have offered 
an explanation, on the basis of temperature and humidity, of - 
the failure of pneumonic plague to become epidemic once a case 
has occurred during the course of an epidemic of bubonic plague. 
Their explanation is as follows: 
We believe we are justified in concluding from these experiments that 
were the plague organisms sprayed under similar conditions they would 
persist longer than cholera vibrios, but a shorter time than prodigiosus 
bacilli. Hence, it seems probable that the plague bacilli contained in fine 
droplets of pneumonic-plague sputum would suffer death from drying in a 
few minutes unless they were suspended in an atmosphere with an extremely 
small water deficit. Infection in pneumonic plague follows the inhalation of 
droplets of pneumonic sputum and obviously the longer these droplets 
remain suspended in the air, the greater is the danger of infection. As 
has just been stated, these fine droplets disappear very quickly except when 
they are suspended in an atmosphere with a very small water deficit. Such 
an atmosphere is under ordinary circumstances of common occurrence in 
very cold climates, whereas it is extremely rare in warm ones. Hence, 
since the droplets of sputum persist longer, the plague bacilli remain alive 
longer in the air, and there is a greater tendency for the disease to spread 
in cold climates than in warm ones. 
The pulmonary lesions in bubonic plague are of three types: 
the ordinary bronchopneumonic form of the aspiration or hypos- 
tatic type, the type of true peripheral infarcts, and a type mani- 
fested by few or many nodules widespread throughout the lung 
which are of metastatic origin. Aside from these focal lesions, 
varying grades of congestion and cedema of the lungs form a 
constant feature of bubonic plague. In the first or ordinary 
bronchopneumonic type of lesion the changes are not macros- 
copically different from a bronchopneumonia due to other 
“his Journal, See. B (92), 7, 172. 
