16 BACTERIOLOGY 



confusing, as scarcely any two authorities agree on the subject, 

 and further knowledge is required before a satisfactory group- 

 ing can be made. 



CHAPTER II 

 HISTOKICAL 



As far as the sciences of Medicine and Public Health are 

 concerned, we have during the past thirty years, as we have 

 already noted, been passing through what may be called the 

 microbiological or bacteriological era, during which for the 

 first time the actual, direct, or exciting causes as apart from 

 those which prepare the soil for, or predispose towards their 

 occurrence of the majority of the diseases to which the flesh 

 is heir, have been, or are in process of being discovered. 

 Apart from such obvious causes as the action of known 

 poisons, physical accidents, cuts, bruises, broken bones, burns, 

 etc., the causation of many diseases is still enwrapped in 

 mystery. The terrible cancer problem still awaits solution. 

 Curious freaks in development are as yet unexplained. The 

 causes of certain errors in metabolism or the chemical pro- 

 cesses of the body and many of its important organs, for 

 example the digestive and the ductless glands, are in many 

 cases still unknown. But during the lifetime of the present 

 generation, the actual causal organisms, bacterial, protozoal or 

 otherwise, of a great number of infective diseases have been 

 discovered and studied. Amongst the more important of these 

 diseases may be mentioned tuberculosis in all its protean 

 forms, typhoid fever, diphtheria, leprosy, cholera, plague, 

 influenza, pneumonia, a great variety of inflammatory con- 

 ditions in different parts of the body, dysentery, malaria, 

 syphilis, sleeping sickness, and many others. Whooping-cough 

 and rheumatic fever may also be added to this list ; whilst it 

 is probably now merely a matter of time for the still unknown 

 viruses of small-pox and vaccination, measles, scarlet fever, 

 chicken-pox, typhus fever, etc., to be isolated and identified, if, 

 indeed, some of these are not already discovered and now 

 merely require definite confirmation. 



Perhaps the first historical foreshadowings of the importance 

 of minute living creatures as a cause of disease are to be found 

 in the writings of Athanasius Kircher, the learned Jesuit, 

 mathematician, alchemist, and Oriental scholar, who, two and 

 half centuries ago, among his other profound studies, included 

 the then infant science of optics. With the comparatively 

 simple magnifying lenses at his disposal, he observed the 

 presence of *' minute living worms " in putrid meat, vinegar, 



