220 STRONG, CROWELL, AND TEAGUE. 



The adrenals sometimes showed congestion. No pathological 

 changes were observed in the pancreas, thyroid, or thymus gland, 

 though the tissues about the latter were usually markedly oede- 

 matous. In the uterus, haemorrhages were frequently observed ; 

 in the other sexual organs or bladder, no special changes were 

 noted. The central nervous system in the instances we had 

 occasion to examine showed no gross anatomical changes with the 

 exception of hypersemia and sometimes oedema of the meninges. 



Bacteriology. — Microscopical preparations and cultures were 

 made from the organs in every case. In each instance the pest 

 bacillus was present in the blood. The bacilli were always much 

 more numerous in the lungs and in the bronchial lymphatic 

 glands at the bifurcation of the trachea than in any of the 

 other organs or in the blood. In the lungs they were found 

 frequently packed together in great masses and were usually 

 pi-esent in pure culture. In but two instances were diplococci 

 encountered in small numbers. The plague bacilli were always 

 more numerous in the spleen than in the blood. In no other 

 disease are such enormous masses of bacteria encountered in 

 the lung. In the tonsil, with but one exception, the number 

 of plague bacilli found was small, usually not more than was 

 observed in the blood. Staphylococci and streptococci and even 

 Gram-positive bacilli were seen in preparations from the tonsils 

 in several cases. In scrapings from the mucosa of the bronchi, 

 plague bacilli were often abundant, but not always so. 



Conclusions. — From the study of the human lesions and those 

 produced experimentally in animals, ^- it would appear that epi- 

 demic plague pneumonia results from inhalation, the primary 

 point of infection being the bronchi. Along the bronchioles 

 the infection extends by continuity directly into the infundi- 

 bulum and air cells, or by contiguity through the walls of the 

 bronchioles to the contiguous tissue of the lung, and gives 

 rise to a consecutive peribronchial inflammation in the tissues 

 immediately surrounding the bronchioles. From these areas 

 the infection rapidly spreads to the adjacent pulmonary tissue 

 and visceral pleura. The bacilli rapidly multiply and produce 

 at first pneumonic changes of the lobular type, and shortly after- 

 wards from the fusion of several rapidly spreading areas more 

 general lobar involvement of the lung tissue. The blood becomes 

 quickly infected, and a true bactersemia results in every case. 

 Secondary pathological changes occur, particularly in the spleen, 

 bronchial glands, heart, blood vessels, kidneys, and liver. The 



'= See IV, p. 173 of this report. 



