146 RECENT RESEARCHES 



95^. But while the adult individuals are killed by a temperature 

 of 120*^ to 176'^, according to their species, the permanent spores 

 have been subjected by Schwann, Pasteur, and Tyndall, to from 

 212^ to 230° without losing their power of germinating. Severe 

 cold does not destroy the vitality of Bacteria : Cohn having ascer- 

 tained that they have recovered after an exposure of several hours 

 to a temperature averaging 8° below zero F. But they are be- 

 numbed at a temperature of 32^ F., losing their power of repro- 

 duction and consequently their action as ferments. 



As before mentioned it is now decided by all the leading bota- 

 nists that the Bacteria belong to the lowest group of the protophytic 

 Fungi — the peculiar characteristic of which organisms is, that, 

 while most plants feed on inorganic or mi?ieral substances, and 

 most animals, on the other hand, on the more complex combinations 

 of the organic world, these organisms live and thrive best on 

 organic matters that are passing down, by decay, into the simpler 

 condition of mineral gases. Hence they are sometimes called 

 Saprophytes (from f^aTrpoe putrid, and <^vtov^ a plant.) 



They form the order Schizomycetes — or Splitting Fungi : and 

 although, in the present state of our knowledge, it is impossible to 

 arrange an accurate classification on a scientific basis, there are 

 five well-marked types into which they may be divided : — The 

 Micrococci, the Bacteria, proper, the Bacilli, the Vibrones, and 

 the Spirilla. 



I. — The Micrococci are minute oval or rounded granules, so 

 small as to be immeasurable— but varying from 1-2 5,000th to 

 1-5 0,000th of an inch in diameter. They are motionless, and either 

 solitary or forming small groups or beads ; and it is probable that 

 some, if not all, the Micrococci are spores of other Bacteria; but 

 as some of them have not yet been known to develop under culti- 

 vation, they must for the present be classed as distinct. 



II. — Bacteria are minute, oblong, cylindrical rods, having spon- 

 taneous movements : sometimes single, but usually attached in 

 pairs, end to end, the pairs being produced by the self-division of 

 solitary cells, they vary in length from i-i 2,000th to i-5,oooth 

 of an inch, and are found to possess flagella ; of which, in the 

 paired state, each has one at its free extremity, while the solitary 

 ones have a flagellum at each end. 



