PART II. 

 PUBLIC HEALTH BACTERIOLOGY. 



TI) ACTERIOLOGY is one of the more recent sciences, 

 -D and is becoming larger and more complex every 

 year. It is now of extreme importance to the Hygienist, 

 as it is also to the Agriculturalist, and in various Arts 

 and Industries. A short glance at its evolution will serve 

 to make the methods and processes to be hereinafter 

 studied more intelligible. 



Leeuwenhoek, a native of Delft, in Holland, produced 

 the first really good microscope and, on examining with it 

 the contents of the intestinal canal in horses, frogs, pigeons, 

 and fowls, and his own diarrhoea stools, he saw small moving 

 and living forms. This was in 1675, and eight years later 

 he examined tartar scraped from teeth, and described 

 and depicted minute organisms such as we recognize at 

 the present day. These discoveries accorded with various 

 theories which were prevalent at the time, and a micro- 

 organismal basis for disease became widely accepted, 

 which, though much the same as prevails now, was built 

 on very slender foundations. Plenciz thereafter insisted 

 on the specific character of the contagious diseases, and 

 explained the incubation period as dependent on the 

 growth of a germ in the body, which had not yet made its 

 presence manifest. Miiller systematized the morphology. 

 Then the theory of spontaneous generation or abiogenesis 

 arose. Dr. Needham boiled a beef infusion, kept it in a 

 well-stoppered bottle, and found that, on keeping, it putre- 

 fied. He argued that the boiling killed all the organisms 

 in the infusion , and that therefore the putrefaction of the 

 infusion pointed to the existence of a special vegetative 

 force which produced fresh organisms. Spallanzani worked 

 at the subject, and found that on boiling for one hour and 

 then hermetically sealing, no putrefaction ensued. It was 

 objected that the air was shut from the vessel, and that 

 this might be necessary. This objection was met by 

 Schulze in 1836 by fitting a flask with right-angled tubes, 



