10 BACTERIOLOGY 



r.s, regardless of their shape alone, the term Bacillus 

 being Preserved for those which resemble a rod in shape. 



Between thirty and forty years ago, when scientists were 

 first turning their attention to this field of research, a some- 

 what heated controversy arose between botanists and zoologists 

 as to whether bacteria belonged to the vegetable or to the 

 animal kingdom, a dispute which is now considered to be 

 settled in favour of the claims of the former. But before this 

 settlement was arrived at, a sort of truce was patched up 

 between the contending parties at the instance of certain 

 French scientists, S^dillot, in 1878, suggesting that the term 

 Microbe (from the Greek mikros^ small, and bios, life), might 

 be used without definitely giving the decision in favour of 

 either party. At the present day this word microbe is still a 

 useful term for describing microscopic organisms both vege- 

 table and animal, or where doubt yet exists as to which great 

 group should contain them. 



A similar use is made of the somewhat popular term Germ 

 (from the French germe, and Latin germen, a bud), which signi- 

 fies merely some rudimentary form of living matter, whether 

 plant or animal. Indeed, the dispute is a somewhat profitless 

 one, as the terms " plant " and " animal " were, of course, in- 

 vented long before these simpler, and practically intermediate, 

 forms of life were discovered. It is an easy matter to distin- 

 guish, say, a cat from a cabbage, or a butterfly from a flower ; 

 but, as we pass lower and lower down the scale, it becomes 

 more and more difficult, and in truth, at the very bottom, no 

 hard and fast line of demarcation can be drawn between the 

 two categories. Bacteriologists are still in doubt as to whether 

 some of the organisms with which they deal should be classed 

 as animal or vegetable ; and their difficulties in classification 

 are now still further increased by the comparatively recent 

 discovery of the existence of certain still smaller living 

 organisms the so-called ultra-microscopic filter-passers, for 

 which the name " Chlamydozoa " has been suggested which are 

 so minute that they are scarcely visible or even quite invisible 

 with the highest powers of the microscope at present available, 

 but which can be proved by experimental methods to be the 

 cause of certain diseases such as smallpox, yellow fever, in- 

 fantile paralysis, foot-and-mouth disease, and other acute in- 

 fective fevers, including in all probability measles and scarlet 

 fever, as well as swine fever, pleuro- pneumonia in cattle, fowl- 

 plague, and other diseases of the lower animals. The exact 

 nature of these filter-passers is not yet established, and it is 

 as yet too soon to speculate as to whether they are bacterial 

 or protozoal, or belong to an entirely new and distinct class 



