194 ORIENTAL PLAGUE chap. 



had been added in the form of gelatine culture remained, 

 during the autumn months, for a long period unimpaired. 

 Indeed, B. pestis was present in a living state in the 

 earth even after seven and a half weeks ; in the sand for 

 six weeks and three days. These are periods of consider- 

 able duration, much longer than were found in the previous 

 experiments (experiment 7) in which the infective materials 

 were exposed to drying during the summer months. In 

 these later experiments of early winter the infective 

 materials were old gelatine cultures, not plague organs, 

 and they were left to dry spontaneously under conditions 

 such as might occur naturally. The fact that plague 

 contagium is, under gelatinous or viscid conditions and 

 during the cooler months of the year, capable of retaining 

 its vitality in sand, and particularly in earth, for a 

 considerable time, is a circumstance having no small 

 importance, seeing that under natural conditions during 

 plague seasons plague expectoration and intestinal mucus 

 charged with masses of the B. pestis cast upon the earth 

 may very possibly in like manner long retain dangerous 

 infective property. 



As a last series I have to mention some experiments 

 in which plague organs were, by themselves, without ad- 

 mixture with other material, exposed to drying, and were 

 then used for feeding rats, both tame and wild. The 

 organs in question — bubo, spleen, lung, and liver, contain- 

 ing abundance of B. pestis — were obtained from animals 

 (guinea-pig and rat) dead of typical acute plague. These 

 organs, after having been cut into fair-sized pieces, were 

 put to dry over sulphuric acid. 



Experiment 20. — The organs of a guinea-pig dead of 



