INTRODUCTION. I 



powerful carnivora) are partially or wholly inoperative the 

 effects are very serious. This is seen to an extent in some 

 Eastern cities in the present day, where dogs go about in 

 bands and prove a great nuisance; also the early 

 Australian colonists had to wage fierce war against the 

 dogs, who bred freely and preyed upon flocks of sheep. 



Liability to disease is directly influenced by the size 

 and functional activity of organs, semi-wild dogs are 

 not predisposed to any special diseases, but artificial 

 selection materially alters the state of affairs. It dis- 

 turbes the wholesome balance which has been by nature 

 established between the organs and systems of organs, 

 and those parts which become especially developed are 

 thereby predisposed to disease. The deleterious effects 

 of domestication are very well marked in the prevalence 

 of nervous disorder and cancer among fancy breeds, of 

 rheumatism among sporting dogs, and of canker of the 

 ear and mange among long-haired and long-eared 

 animals. Almost all the disorders of dogs thus arise 

 from man's mismanagement and tampering with natural 

 conditions. Disease is not a necessary attendant on 

 variation, but the latter must be considered a most impor- 

 tant predisposing cause. 



We must accept as established by observation the 

 following statements : — That carnivora among mammals 

 have, as such, some special features of disease ; dogs among 

 carnivores, different breeds among dogs, and individual 

 dogs among those of a breed ; or, in other words, order, 

 genus, species, variety, and individual, influence the type 

 and character of disease. 



Want of care in regulation of surrounding influences is 

 a fruitful cause of disease ; by gradual change the con- 

 stitution may become adapted to the most varied condi- 

 tions of diet, climate, and work, but -sudden transitions 

 throw the animal economy into disorder. Thus the dog 

 has almost become a herbivore in some cases, and indeed 

 generally is an omnivore ; so greatly has the influence of 

 changed diet affected the system that the very teeth are 

 altered accordingly ; but if we suddenly change any dog 



