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EECENT RESEAKCHES 



owing also to their action that the continuation of life is possible 

 on the globe. 



We now come to consider what is, practically, the most impor- 

 tant part of our subject, namely, the connection of the Bacteria 

 with disease. 



Some years ago it was the current belief that epidemic diseases 

 generally, were propagated by a kind of malaria, which consisted 

 of organic matter in a state of what was known as tnotor-decay ; 

 and that when such matter was taken into the body, through the 

 lungs, skin, or stomach, it had the power of spreading there the 

 destroying process which had attacked itself; much as fermentation 

 is produced by the presence of yeast. But when in 1837, Schwann 

 and Cagniard de la Tour discovered the yeast plant, and subsequent 

 observers discovered the connection between putrefaction and the 

 Bacteria, the idea was gradually evolved that these organisms 

 might also be concerned in the propagation of the contagious or 

 zymotic diseases. 



To no one are we more indebted for our knowledge in this 

 field of medical study than to Pasteur, not only through his own 

 immediate experiments, but also for the new direction he has 

 given to scientific discovery, the new clues, and new paths of 

 research which he has opened out. Closely following Pasteur in 

 careful and original research comes Koch, who when only a young 

 physician in a small country town in the neighbourhood of Breslau, 

 made a world-wide reputation by his masterly investigations, 

 causing him to be transferred to the post of Government-adviser 

 to the Imperial Health Department of Berlin. Many other obser- 

 vers are also doing good and careful work, striving to detect 

 the presence of Bacteria in different diseases ; and, when found, 

 working out their life-history, and daily adding to our knowledge 

 of the subject. 



The microscope is, of course, our main aid in the study ; and 

 considering the extreme minuteness of the Bacteria, it is only by 

 the use of the most perfect instruments that we can expect to learn 

 anything about them ; and none but highly trained microscopists 

 are likely to deduce accurate results from their observations. Not 

 only on account of their minuteness, but also because they frequently 

 have the same refractive index as the fluid which contains them. 



