SCHIZOMYCETES AND SACCHAROMYCETES 291 



The term " Microbe " has been employed, in a general sense, 

 by the French, and adopted from them to indicate all the 

 minute organisms which are now recognised under Schizo- 

 mycetes and Saccharomycetes, 

 whilst in many cases the 

 former are often spoken of 

 simply as " Bacteria " and the 

 latter as "ferments." These 

 " bacteria " appear " in liquids 

 examined under the micro- 

 scope as small cells of a spheri- 

 cal, oval, or cylindrical shape, ^jr<©S>- ^ ^ 



sometimes detached, some- Fia. 135.— Bacterium termo. Chatto and 



times united in pairs, or in Wmdus. 



articulated chains and chaplets (Fig. 135). The diameter of 

 the largest of these cells is two micromillimetres and that of 

 the smallest is a fourth of that size, so that at least 500 of the 

 former and 2000 of the latter must be placed end to end in 

 order to attain the length of a millimetre. It is therefore 

 plain that a magnifying power of 500 to 1000 diameters, or 

 even still higher, is required to make these beings clearly 

 visible under the microscope." * 



Besides the vegetative multiplication of these cells in one, 

 two, or three directions, there is a double method of formation 

 of spores, which must be described. So long as all the con- 

 ditions remain favourable to growth and vegetative develop- 

 ment, only vegetative multiplication prevails. If the cells 

 can obtain sufficient food, and the food is of exactly the right 

 kind, the rate at which they grow is marvellous. " Cohn cal- 

 culated that a single germ could produce by simple fission 

 two of its kind in one hour, in the second hour these would be 

 multiplied to four, and in three days they would, if their 

 surroundings were ideally favourable, form a mass which can 

 scarcely be reckoned in numbers — or if reckoned, could scarcely 

 be imagined — 4772 billions. If we reduce this number to 

 weight, we find that the mass arising from this single germ 

 would in three days weigh no less than 7500 tons. Fortu- 

 nately for us, they can seldom get food enough to carry on this 



1 Microbes, Fertnents, and Moulds, by E. L. Trouessart, Loudon, 1889. 



