CHAPTER XVI. 



Lung Plague in Cattle, and Cholera in H(jgs. 

 The Conditiotis leading to the Origin of these Diseases. 



That some cattle are susceptible to diseases of the lungs 

 in consequence of changed conditions in themselves 

 and in their surroundings, is well known; and that they 

 are more susceptible to lung diseases, the further their ne- 

 cessary conditions of breathing are unfavorably changed, 

 is indisputable. Oxygen is the leading necessary of life 

 to all breathing, locomoting animals ; and this is conspic- 

 uously true of such farm stock as cattle and swine, a fact 

 with which practical farmers are familiar. 



A leading natural condition of cattle and swine, is con- 

 stant out-door activity in gathering their daily food. This 

 regular out-door activity increases the supply of oxygen in 

 the blood ; and the rate of breathing and extent or quan- 

 tity of oxygen in the blood, which daily out-door exercise 

 causes and supplies, is the necessary or natural rate and ex- 

 tent of breathing, which completes and supplies the neces- 

 sary quantity and proportion of oxygenated blood con- 

 veyed by the arteries. 



Breathing completes the blood, by suppyling the oxygen 

 which causes all the red blood to circulate. So the quan- 

 tity of blood that circulates, is made to circulate by its 

 oxygen, and the extent of the blood circulation corres- 

 ponds with the extent of breathing ; which latter — when 

 above the minimum of inaction — is according to the ex- 

 tent of out-door exercise. 



That the out-door exercise of many thousands of cows 



