314 THE DOa IN DISEASE. 



learn in regard to predisposing causes, and the real patho- 

 logical lesion, if there be such visible by the microscope ; 

 while we are utterly in the dark as to any method of treat- 

 ment that has the slightest effect when once the disease 

 is established. 



Eabies may be regarded as a specific disease of the 

 nervous system leading to a fatal issue, and in the course 

 of which all the various functions of the body may be 

 more or less abnormal though the psychical changes are 

 the most pronounced. 



The cause is a virus or poison communicable by a bite 

 from the affected animal owing to the poison being in the 

 saliva. It is known that inoculation with the saliva will 

 produce the disease. 



Protection {immunity) against rabies has been pro- 

 duced by Pasteur by inoculations of the weakened {attenu- 

 ated) virus obtained from the portion of brain next to the 

 spinal cord {medulla oblongata). 



The period of incubation or latency of the disease is 

 more variable than in the case of any malady known to us. 

 It seems to vary between a few days (ten to fifteen) and 

 many months, if not even years. 



The animals affected may show symptoms that vary 

 sufficiently to warrant a division into two distinct forms — 

 the excitable, furious, or maniacal, and the paralytic. It is 

 to be borne in mind, as said before, that in this, as in all 

 diseases, absolutely typical cases are rare, and the dog may 

 be sick unto death with either form and not attract very 

 marked attention. Death usually results in from two to 

 ten days in the furious form, and in a much shorter 

 period in dumb rabies. 



