34 MISCELLANEOUS PAPERS ON APICTJLTUEE. 



ETIOLOGY (CAUSE) OF DISEASES. 



Every abnormal condition in the body of an animal which we 

 know as disease has a cause which has brought about such a condi- 

 tion. In most of the diseases of man and the higher animals compar- 

 atively little is known of the cause Likewise, and unfortunately, 

 the same is true of bee diseases. Gradually but slowly new facts 

 about all diseases are added to our knowledge, the unfortunate thing 

 being that so man}^ statements are reported as facts which have never 

 been demonstrated to be true. 



In the study of the etiolog}^ of a disease and in the discussion of it, 

 it is convenient to divide the causal factors into predisposing and 

 exciting. Under the predisposing causes which may be considered 

 as factors in bee diseases we have age, sex, race, heredity, climate, 

 and preexisting disease. Under the exciting causes we may consider 

 food and micro-organisms. 



To illustrate, let us consider the different factors just mentioned. 



PREDISPOSING CAUSES. 



Age. 



In our experience with human diseases we have learned to expect 

 scarlet fever, measles, mumps, and whooping cough more often in 

 children than in adults; typhoid fever and appendicitis in young 

 adults; a::d cancer in those more advanced in life. In bee diseases 

 we expect European foul brood to attack larvae that are younger 

 than those which suffer from American foul brood. TTe expect the 

 so-called " pickled brood " to die just before or after capping, while 

 paralysis is, as far as we know, a disease of adult life. 



Sex. 



Of some importance in the etiology of human diseases is the factor 

 sex. Inflammatory rheumatism, gout, and diabetes, for example, 

 occur more frequently in men, while goiter and hysteria are more 

 frequent in women. In bee diseases we expect in American foul 

 brood to find the worker larvae more often attacked than the drone, 

 while in European foul brood this difference, if it exists, does so 

 only to a slight degree. 



Heredity. 



You are all familiar with the fact that heredity is considered as 

 an important predisposing factor in tuberculosis, cancer, gout, in- 

 sanity, etc. It is interesting that in the so-called " pickled brood " 

 there is some evidence which indicates that heredity plays an im- 

 portant role. 



