118 JOURNAL OF THE [November, 



In his investigations, the microscope, if used by him, was used 

 simply as an adjunct. That instrument might show what algae 

 were present discoloring the water and giving off bad odors, but 

 it was subordinated to the chemical analysis. Meantime, how- 

 ever, the study of bacteria, particularly of bacteria in water, 

 began to occupy the attention of students, and when it was 

 found that the nitrogen and ammonia discovered in water by 

 the chemists were not the causes of diseases such as typhoid 

 fever, the theory was advanced that those diseases were caused 

 by bacteria germs ; for example, typhoid fever by a typhoid 

 fever germ, cholera by a cholera germ. Pasteur and Koch were 

 relied upon as authority for such theories, and it was claimed 

 that in Germany far better results could be obtained in the ex- 

 amination of water for impurities by means of the microscope 

 than by any chemical analysis, upon the ground that the germs 

 of disease, bacterial in their nature, were undiscoverable except 

 through the microscope. Hence, the existence of bacteria in 

 water, their propagation, functions and effects, have become 

 questions of the utmost importance, more perhaps because of 

 what has been said concerning them than of what has been 

 done. As all the new processes of analyzing water by biological 

 methods depend upon the cultivation of bacteria in water, 

 a few words about bacteria in general may not be inappropriate. 

 The bacterium is the lowest of organic forms. Its place in 

 nature is on the boundary between animal and vegetable 

 life. Van Leuwenhock made it known to science two hundred 

 years ago. In examining with a microscope the tartar from his 

 teeth, he found it swarming with actively moving minute organ- 

 isms. These were bacteria ; and their number was as great in 

 the mouth of every human being, so the discoverer thought, as 

 the population of the habitable globe. At that time spontaneous 

 generation was a subject of discussion, and the bacteria were 

 studied with a view of elucidating it. Later, it was ascertained 

 that these living forms abound in the atmosphere, and that they 

 will not generate in preparations from which the air is excluded. 

 Pasteur has demonstrated the impossibility of spontaneous gen- 

 eration. In his studies of atmospheric germs he worked among 

 bacteria and separated them into classes. He also studied 

 them in connection with disease. In this field of investigation 

 the Germans are now the most advanced students. 



