no SCIENCE PROGRESS. 



rapidity with which this is done either in an exsiccator or 

 by exposure to varying temperatures dermines the result. 

 At 29°-3i° C. the bacilli are killed in four and a half days, 

 and in three hours if dried over sulphuric acid. When the 

 drying process is slow and carried out in the dark at 

 i6°-20° C. living bacilli are found on the thirtieth day. If 

 in Hong Kong at a temperature of 28°-3i° C. four and a 

 half days is needed, then for our climate about ten days 

 would probably suffice to kill the microbe. Direct sun- 

 light and dry heat destroy cultures of the bacillus with 

 certainty, but steam at 50 C. for one hour renders all 

 cultures harmless, and the following table by R. Abel show 

 this to be a most effective means of destruction : — 



At ioo° C. all bacilli dead at the end of 1 min. 



j) °° j; >> »> 5 ') 



o 



); 7° )> " " IO »' 



„ 6o° ,, ,, ,, 20 „ 



,, 50 ,, some alive, some dead at the end of 30 min. 



,, 50 ,, all dead ,, ,,' 60 ,, 



The pest-bacillus is pathogenic for man and a great 

 number of animals, especially mammals, though the symp- 

 toms, progress and termination of the disease are not quite 

 similar in both cases. Gaffky, R. Pfeiffer, Dieudonne 

 and Sticker (25), members of the German Plague Com- 

 mission recognise three different clinical varieties of the 

 plague. In the true bubonic plague there is a sudden 

 onset of high fever accompanied by characteristic swellings 

 of the superficial lymphatic glands in the groin and the 

 axilla, which form the buboes of typical plague and contain 

 almost pure cultures of specific bacilli with or without the 

 association of pyogenic streptococci. Pest-septicseinia is 

 another form of the disease where the spleen is always 

 enlarged and signs of general sepsis with haemorrhages 

 into the stomach and bowels are found on autopsy. 

 The third form of plague is Pest -pneumonia in which 

 numerous specific microbes can be recognised in the 

 sputum either alone or associated with diplococcus 

 lanceolatus and pyogenic streptococci. Among human 

 beings the mortality is as high as 80 per cent. After an 

 incubation period which is stated by Lowson (16) to be 



