DEPARTMENTS OF BACTERIOLOGY 21 



impossible for us now to foresee what more wonderful dis- 

 coveries in this domain may still lie ahead of us. 



Some diseases which have hitherto baffled our attempts to 

 unveil their causes, are now known to be due to living organisms 

 so minute that they cannot even be seen by our present-day 

 microscopes, powerful as these are. Yellow Fever, Infantile 

 Paralysis, Foot-and-Mouth Disease, are among the number of 

 these. But recently the successful cultivation of the organism 

 causing the second of these diseases has just been announced 

 in New York ; and it remains to be seen whether advances in 

 the resources of optical and chemical science and experiments 

 on animals will lead to the discovery of the nature of these at 

 present " ultra-microscopic " germs, and how they may be dealt 

 with for our protection. 



CHAPTER III 



THE SCOPE AND DEPARTMENTS OF BACTERIOLOGY 



THE field of General Bacteriology is so vast and complex, so 

 ever broadening, that no single individual is now able to deal 

 with it in all its branches, and there has therefore been an in- 

 evitable tendency for it to be split up into special great sub- 

 divisions or branches ; and even these main subdivisions are so 

 extensive that, in all probability, they too will in turn in the 

 future undergo further subdivision among specialists, each 

 with a particular knowledge of his own and a general knowledge 

 of his colleagues' fields of labour. 



At present we may recognise the following main subdivisions 

 of bacteriology, each to some extent overlapping the other, but 

 each in itself affording a definite field of research. 



Medical Bacteriology may be placed at the head of the list, 

 as ft has been the pioneer leading the way in the development 

 of the whole science, and along with it may be included the 

 special fields of Dental and Veterinary Bacteriology. Medical 

 Bacteriology has itself come to be subdivided into two great 

 fields, Pathological Bacteriology, the study of organisms in 

 relation to the methods of causation, the processes, and the 

 treatment of disease in man and animals, on the one hand : and 

 Hygienic, Public Health, or Sanitary Bacteriology, the study 

 of the mode of spread of such organisms, their presence in food 

 and in air, water, soil, sewage, etc., and the prevention of 

 disease by the methods of Public Health, State or Preventive 

 Medicine on the other. The practical application of a know- 

 ledge of bacteriology is also required, not only for Sanitary 



