46 A RARE BACILLUS. 



to about 1 per cent., and the shelves to be wiped over with it. 

 This was done and the bacillus vanished, the cure being 

 instant and complete, the cost and the trouble practically 

 nothing, while from its harmless and non-poisonous nature, 

 there was no disturbance to anything, always excepting the 

 bacillus. 



Perhaps it may be well here to state that the term 

 bacillus is applied to those micro-organisms which are rod 

 shaped, differing from bacteria in degree rather than in kind, 

 and reproducing their species by simple sub-division. Their 

 minute size may be imagined from the fact that Cohn 

 estimates that it would require 40,000 millions of bacilli to 

 weigh one grain. The rate at which they multiply is about 

 as difficult to realise, for many of them are capable of 

 reproduction every hour, thus one bacillus may become 

 sixty-four at the end of six hours, and in a day at this rate 

 of increase there would be something like four millions, and 

 in three days about 4,772 billions, a number perfectly 

 incomprehensible. It is computed that under similarly ideal 

 conditions the single and practically weightless bacillus is 

 capable in the same time of producing an aggregation of 

 bacilli weighing no less than 7,500 tons, so I think you will 

 admit that the name prodigiosus may be appropriately applied. 



This particular bacillus is termed chromogenic, that is 

 it produces colouring matter, in this case a brilliant red. 



Under the microscope it is seen that this pigment does 

 not permeate the whole mass of the germ, but resides 

 merely in the outer sheath, which envelopes a living mass of 

 grey-coloured protoplasm. Let it be remembered that bacilli 

 are fungi of the lowest known type, plants in fact from 

 which the green colouring matter (chlorophyll) is absent. 

 The chromule, as any other such colouring matter is called, 

 of the bacillus prodigiosus, is capable of being extracted by 

 ether, and is only formed when the bacillus is living under 

 suitable conditions as to food and temperature. It is, 

 however, possessed of astonishing vitality, for an exposure 

 to a temperature of 158°-176° F. (70° to 80° C) is effectually 

 resisted, and it requires at least half-an-hour's exposure at 

 the temperature of boiling water for its complete destruction 

 by heat. 



The red colouring matter is developed best at blood 

 heat, but disappears if the bacillus be cultivated on one 

 kind of nutrient medium for any length of time, though it 

 may be again coaxed into full tint by a diet of potatoes, on 

 which it seems to nourish exceedingly well in our climate. 



