16 MICHIGAN ACADEMY OF SCIENCE. 



compounds are poisonous. Neither do we theorize when we say that 

 the anthrax bacillus produces anthrax, the tetanus bacillus tetanus,' 

 the glanders bacillus glanders, the hog cholera bacillus hog cholera, 

 or the tubercle bacillus tuberculosis. These and others have been proven 

 to produce these diseases, not once, but hundreds and thousands of times. 

 Every student in a bacteriological laboratory becomes personally ac- 

 quainted with these disease producing organisms and with their action 

 in the animal body. 



In order to prove that an organism is the cause of a given disease, it 

 is necessary to comply with certain requirements. 



Briefly stated, these are as follows: First, the specific organism 

 must be present in every case. Merely to be present does not prove that 

 it is the cause as it may be an accompaniment or a consequent of the 

 disease — a. possibility, which, though extremely improbable, must never- 

 theless be conceded. Secondly, this specific organism must be 

 isolated in a perfectly pure form, free from all other organisms and 

 foreign substances. In other words a pure culture must be obtained, just 

 as the chemist before applying his final tests, isolates the substance in 

 a condition of chemical purity. Thirdly, the pure culture of the organism 

 when properly introduced into a susceptible animal must produce the 

 disease. 



If these requirements are satisfied it is evident that there is no escape 

 from the conclusion that that special organism is the cause of that dis- 

 ease. Demonstrations of this kind have been furnished in a very large 

 number of diseases of man, of animals and even of plants. Anthrax in 

 cattle and in man was the first disease shown to be due to bacterial origin. 

 And it may be perhaps of interest to add that the last disease which has 

 been proven to be due to bacteria is the recent plague in China, which 

 is the same as the plague which devastated Europe in the pre- 

 ceding centuries under the name of black death. This interesting 

 demonstration has been simultaneously and independently achieved by 

 Yersin of Paris and Kitasato of Tokio. 



The fact that bacteria produce disease is unquestionably an important 

 one. But of much greater significance to man are the results which 

 necessarily follow. As long as such diseases as cholera, typhoid fever, 

 tuberculosis, diphtheria were supposed to hSve some obscure ill defined 

 cause, it was well nigh impossible to successfully combat these diseases. 

 With the demonstration that bacteria are the cause is furnished some- 

 thing that is definite and tangible. 



These organisms can now be isolated and artificially grown and their 

 weak points, so to speak, readily ascertained. In this way it becomes pos- 

 sible to establish a rational method of prevention of the communicable 

 diseases. The great advances which have taken place in sanitary sci- 

 ence during the last quarter of a century are directly the outcome of the 

 study of bacteria. Thousands of lives have been saved through the facts 

 disclosed by the investigation of these organisms. The scientific pre- 

 vention of disease can be seen nowhere as well as in brilliant achieve- 

 ments of surgery. 



To Joseph Lister is due the credit of having utilized the facts gathered 

 by Pasteur on fermentations, and of having applied these facts to surgery, 

 long before a single germ was actually proven to be the cause of a disease. 



