DISEASE GERMS 



4. Work at the Pasteur Institute 



Professor Elias Metschnikoff was busy, when I saw him 

 at the Institut Pasteur in Paris last September, with an 

 experimental investigation of " appendicitis." He finds 

 that chimpanzees can exhibit this disease, and he is led 

 by experiments on those animals to believe that a gas- 

 producing micro-organism the bacillus aerogenicus 

 already known as occurring in the human intestine is 

 especially active in exciting the disease. Parasitic 

 worms or other foreign bodies must first wound the 

 delicate lining of the appendix before the virulent gas- 

 forming bacillus can penetrate and start inflammation 

 and abscess. Metschnikoff was also investigating a 

 disease of tropical regions, known as " the Yaws." Most 

 people would imagine that this name refers to a disease 

 like the gapes, but it is quite different, being an ulcera- 

 tion of the skin caused bv a spirillum. 



Spirilla corkscrew-like threads of excessive minute- 

 ness are parasitic organisms, like bacteria, bacilli, and 

 micrococci. They are of different kinds some harm- 

 less, some deadly. One is common in the mouth of the 

 healthiest of us another causes one of our most terrible 

 diseases. They can be distinguished by the microscope, 

 though much alike. What microscopists call "dark- 

 ground illumination" that is, illumination by hori- 

 zontal rays of light, obtained by a prism attached 

 below the glass slip on which the object is placed for 

 examination with the microscope, has been found at the 

 Institut Pasteur to be a very ready way of showing the 

 spirilla in fresh blood or sputum. The spirilla are alive, 

 and are seen when highly magnified, shooting rapidly 

 across the field of view with a corkscrew action, like 

 brilliant silver threads. The detection of the microbe 

 which causes an infective disease, is often the first step 



