Rheumatism. 539 



matic parents are more obnoxious to the disease in the ratio of 

 5 to I. In the. absence of data for animals, we may say that it 

 is probable "that the influence of heredity will hold good for live 

 stock in this matter. Whether th.e disease results from faulty 

 metabolism or from microbian invasion or toxins, the hereditary 

 defensive powers of the animal cell are likely to be an important 

 factor. 



Age. Genuine rheumatism is not common at a very early age, 

 but in animals as in man, attacks especially those in the prime of 

 life, accustomed to vigorous exercise, free perspiration and suc- 

 ceeding chills. There is as yet no direct evidence of an exhaus- 

 tion of the susceptibility of early maturity and of any consequent 

 immunity of the old. 



Cold and damp. The association of rheumatism with cold and 

 damp has always been so notorious that no argument is needed 

 to enforce the truth. It is pre-eminently the disease of cold 

 climates and cold situations exposed to the north and east in 

 Europe, or to the north and west in North America on the At- 

 latic slope. It is very little prevalent in the tropics. Buildings 

 and yards that lack sunshine and exposed storm-swept hillsides 

 show cases most numerously. Dogs kept in cold, damp sunless ^ 

 cellars often suffer. Cold, damp or frosty nights start or aggra- 

 vate cases in animals left out in the field, while warm sunshine 

 usually brings immediate improvement. A sudden change of 

 weather to cold and wet is the signal for aggravation of the exist- 

 ing disease, though this may have set in before the change of 

 weather has been fully developed. I^ate autumn and early spring 

 with their sudden changes, their sleet and rain are especially 

 hurtful and particularly to chronic cases. The cold, raw ocean 

 winds on the Pacific coast contrasting with the warm sunshine is 

 a marked contributing cause. The currents of cold air that draw 

 up through shaded valleys, gullies and ravines expose their 

 denizens to attacks. Rheumatism is more rare among well 

 housed and carefully treated family horses, and less so in draught, 

 dray and other hard working horses that are made to cross 

 streams and stand with feet and legs in cold water while the; 

 body is drenched with perspiration. Dogs suffer in the same 

 way while hunting. Haycock attributes many attacks to wash- 



