74 



effects and not directly to the presence of the bacilli. In fact, 

 even in the large hemorrhagic areas of the lymph glands bacilli 

 were practically absent, though they abounded in the neighboring 

 ones formed by the fixed tissue elements. Stress is also to be laid 

 upon the fact that these organisms, as a rule, were not found in the 

 blood vessels of the sections examined. The perforating ulcer of 

 the soft palate, surrounded by cicatricial tissue, in connection with 

 the defective incisors, suggested the diagnosis of syphilis heredita- 

 ria tarda. It appears that the chronic syphilitic perforating ulcer 

 became the portal of entrance for the plague virus, 



INSECTS AS PLAGUE CARRIERS. 



Among the plague cases investigated there is one in which it 

 appears probable that the infecting bacilli were carried into the 

 body of the patient — a child — by Pediculi capitis. It is advisedly 

 stated that this mode of infection appears very probable, because 

 it is naturally impossible beyond doubt to be certain as to such an 

 occurrence. Only experimental trials on human beings could firmly 

 establish the possibility of this mode of transmission; but such 

 tests with plague bacilli are of course inadmissible. 



The question whether insects, and particularly parasitic ones, 

 play a more or less important role in the spread of plague is still 

 far from being definitely settled, as the views of investigators and 

 writers upon this subject are diverse. 



Among the modern workers on plague who first gave their attention 

 to insects as plague carriers is Hankin, who reports on a long series 

 of researches on the relation of ants having fed upon rats dead of plague 

 to the possible spread of the disease. He found that ants neither die 

 from plague nor retain the infection for any length of time. By pre- 

 paring extracts of ants shortly after they had fed upon rats dead of 

 plague, Hankin obtained a fluid which, when injected into rats and mice, 

 would kill and produce typical plague lesions in these animals. 



Ogata, in studying a plague epidemic in Formosa, took seven fleas from 

 a rat dead of plague, crushed them between sterile slides, and injected 

 the material so obtained into two mice, one of which died, while the 

 other remained well. 



La Bonadiere and Xanthopulides, as they maintain, by cultural methods 

 demonstrated the presence of plague bacilli in a mosquito ( ?) (moustique) 

 which had bitten a patient sick with plague. 



Simond is inclined to attribute much importance to rat fleas as plague 

 carriers. In fleas taken from rats infected with the disease he foimd 

 bacilli siinilar morphologically to those of plague. He inoculated three 



