PRESIDENTIAL ADDRESS XV 



bodies, Avoultl soon cut oft" the food supply of new plants and 

 animals ; life would be impossible, because the work of death 

 would be incomplete ; or, as Pasteur puts it, because thfe return 

 to the atmosphere and to the mineral kingdom, of all that which 

 has ceased to live, would be totally suspended." 



While the poisonous products of bacterial action on living 

 material are, as already stated, termed t(i.n>is .- similar products, 

 due to micro-organic decomposition of dead material, are known 

 as ptonitiiiies or cadaveric alkaloids, and many of these have 

 been separated and experimented with, and putrid infection, or 

 better, iitoxiainea poisoning, is by no means uncommon, and is, 

 in general, due to the consumption of tainted meats, tinned 

 foods, &c. 



Chromogenetic, or Colour-forming bacteria, are organisms 

 which during their growth, elaborate or secrete colour stuff. Expose 

 a boiled potato, or some bread, or other farinaceous article, to the 

 air of any ordinary room for a few days, and colonies— as they 

 are termed — of various moulds, yeasts, and bacteria will develop, 

 and the colours of these may be very various. A bright blood 

 red patch may be seen, this is a growth of the JJacillns pnxli- 

 f^iosm, a micro-organism having remarkable characteristics : some- 

 times its appearance is prevalent ; in Paris, in 1848, it attacked 

 the bread in the military bakehouses. It has not infrequently 

 been found on the sacred wafer, and by its sanguine colour has 

 given rise to the appearance known as the " bleeding host," a 

 phenomenon taken advantage of by the m iracle monger to appall 

 the ignorant and superstitious crowd. As Fraenkel says, "All 

 the cases of miraculous blood-covered bread, weeping hosts, &c., 

 which are reported, may be safely referred to this bacterium, as 

 may also those in. which the reddening of bread was supposed to 

 result from diseased corn, and the reddening of milk from a 

 special^ disease of the cows." 



Colours, other than red, maybe produced: — Yellow, by various 

 kinds of Sarcincp. '*'') Yellowish green to blue by the Jiacillus 

 Pyoeyaneiis, which discolours the pus and bandages of a wound, 

 making them blue; and the BociUus of blue milk, the 

 B. ('[janoiimm. Purple to violet by the Hacillus Violaccus, 

 or lanthinus. '48) Red by the Hocillns Indicus. <«) This 

 is historic. — It derives its name from its having been 

 found by Koch in the intestines of an Indian monkey when 

 he was in India, seeking the cause of cholera. It has the 

 faculty of resisting for a long time various deleterious in- 

 fluences. For instance, a small quantity of potato culture 



