^August, 1907.] Fijtli Convcniioii, Cliaiiiber of Agriculture. 489 



more suitable for sheep than either cattle or horses and that good cattle 

 country is not necessarily good horse country. Unusual seasons too, which 

 affect the ordinary food and water supply, also upset all our calculations. 



We have commenced an era of closer settlement which entails a more 

 restricted form of domestication for our animals, and it becomes necessary 

 to have all kinds of farm stock on the same land. This may result in 

 a larger number of diseases making their appearance. The more restricted 

 life reduces the animal's choice of food and water, and the conditions of 

 existence become more artificial than ever. We produce animals more 

 suitable to our requirements, but the balance between adaptation and 

 environment becomes more difficult tO' maintain at everv stage. Is it then 

 anv wonder that veterinarv science is taxed to the utmost and may fail 

 to point at once to the exact cause of a disease or the best way of avoiding 

 it? The mischief is done before the disease declares itself and the changes 

 required take time tO' accomplish. 



It is to such problems as these that the best efforts of the scientists 

 are being directed. Stock-owners should study the causes of disease. Thev 

 have better opportunities of doing sO' than veterinarv surgeons. Close 

 observation is needed to get definite information. We have to remember 

 that when external influences exceed the limits of endurance disease is 

 the inevitable consequence. Whether harm will result depends upon the 

 inherited potentialities of the animal, the functional activity of its cells, 

 and its protecti\e and regulative mechanism. Sensiti\enes& to noxious in- 

 fluences is known as susceptilnlity or predisposition, resistance to disease 

 as immunity. Resistance differs in different species of animals, in different 

 animals of the same species and in the different organs and tissues of the 

 same animal. Fortunately, we find that domestic animals possess great 

 .adaptability- — the same species surviving the rigours of a Canadian winter 

 or a tropical summer. This adaptabilitv is greatlv aided by man's intelli- 

 gent care. If he did not provide winter food and shelter the majority 

 would probably succumb. 



Wild animals collected in zoological gardens suffer more from change 

 of climate and surroundings, and it is only with difficulty that some of 

 them can be kept alive even for a short time. In all outbreaks of infectious 

 diseases there are always a few animals that remain unaffected or are so 

 slightlv affected as to recover and live to perpetuate their species. Some 

 diseases affect one species only, while others are easily transmitted to 

 animals of other species. Pleuro-pneumonia in cattle, strangles in horses, 

 distemper in dogs are examples of the former ; tuberculosis, anthrax and 

 rabies represent the latter. 



The resistance of different tissues is exemplified in certain diseases 

 always attacking certain organs or parts and not others. Pleuro-pneumonia 

 for example attacks the respiratory organs only, while tuberculosis may 

 invade any part of the organism. 



Whilst such predisposing causes as hunger, starvation, bad or unsuitable 

 food and water, over feeding, over exertion, excessive breeding or milking, 

 absence of shelter, wounds and injuries, parasites such as ticks and intes- 

 tinal worms, exist, disease will continue to exist in spite of the best efforts 

 of the veterinarian. These are the dangers to be avoided if disease is to 

 t)e prevented or eradicated. 



What Experience Teaches. 

 Practical experience teaches the stock-owner that certain breeds of 

 •cattle are suitable for certain districts whilst others are less so. Avrshire 



