456 Transactions of the Society. 



resist extreme cold, and in the case of seeds and chestnuts they 

 are said to have survived the exposure to the very low temperature 

 of —100° C, and very lately in experiments by Messrs. de Candolle 

 and Pictet the refrigeration was carried to — 80° C, the seeds 

 germinating afterwards. I think experiments have also been 

 made on hybernating animals, but I do not remember the exact 

 temperature destructive of life. The minuteness, however, of the 

 Bacteria almost forbids comparison with the other objects. 



Such details I fear must be sadly wearying to those who take 

 no special interest in the study of these micro-organisms, and to 

 such I offer every apology. Nevertheless, I would ask them 

 to try and estimate carefully the value of the study of these 

 ubiquitous objects. They set up minute changes in some of the 

 articles of our dietary as either invite or repel the organs of smell 

 and taste. The numerous varieties found by M. Duclaux in the 

 imperfect making of Cantal cheese, at once point to a large field 

 of inquiry among the articles that are in our daily diet. They 

 play a vast role as the grand scavengers in the silent destruction 

 of lifeless forms and are thus beneficent agents; they are the 

 companions of our life and accompany, if they do not originate, 

 many depressing and fatal diseases, multiplying so rapidly in cases 

 of lowered vitality of their host that they kill by their numbers, 

 or perhaps by depriving the nutrient fluid of part of its oxygen, 

 though this, as pointed out by Mr. Dowdeswell in his excellent 

 article upon Septicaemia,* seems, in the smaller forms at least, 

 improbable. The chemical changes induced by their own require- 

 ments may furnish noxious matters detrimental to the life of the 

 higher organism — and harmless forms under new conditions may 

 perhaps acquire such virulent properties, that in the state of 

 spores the minutest quantity suffices when inoculated into the 

 connective tissue of a healthy animal, if such have not acquired 

 previous immunity, to cause severe illness if not certain death. 

 Their importance, as affecting, on a vast scale, the life of man 

 and of animals, invests them at least with the symbol of respect.! 



It is only by cultivation that we can hope to distinguish the 

 living from the lifeless, for may we not have before us in such as 

 are gathered from the air, some that are dead, and some of what 

 Dr. Phipson calls "fossil forms." Morphologically their resem- 

 blances may be so great that their differences are to our powers other- 

 wise indistinguishable. Possibly some may be inert when cultivated 

 in one fluid, and highly poisonous in another — as in living bodies. 



* Quart Journ. Micr. Sci„ xxii. (1882) p. 66. 



f M. Miquel found by the statistics of the mortality that occurred last year at 

 Paris, that there were nine rises which closely corresponded each to a rise in the 

 number of Schizophytes found in the air. He merely points out the interesting 

 coincidence. 



