CHAPTER XXIII 



DISEASES WHOSE MICROBIC CAUSE HAS NOT BEEN 

 ISOLATED 



THERE yet remain a number of diseases for considera- 

 tion which are most certainly of microbic origin. The 

 causative germs, however, have not been isolated and 

 subjected to Koch's rules. The list of such diseases is 

 growing shorter every year. 



HYDROPHOBIA 



Definition. An infectious disease communicated by 

 the bite of an animal and characterized by severe nervous 

 disturbances and spasms, especially of the muscles of 

 respiration and deglutition. 



Etiology. This is probably due to a specific micro- 

 organism which has not yet been isolated. All mammals 

 are susceptible to the disease. The mode of infection 

 is probably always through the bite of an infected 

 animal, usually the dog, though cats, wolves, horses, 

 and cattle may convey the disease. 



Morbid Anatomy. There is congestion of the cord and 

 brain, as in tetanus, and some exudation in the perivas- 

 cular tissue. Congestion of other organs may occur, as 

 of the gastro-intestinal tract, respiratory system, and 

 kidneys. The only characteristic feature is the pres- 

 ence in the large nerve-cells of the central nervous sys- 



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