TIIE LUNG PLAGUE. 23 



THE ALLEGED ORIGINAL CAUSES OF THE LUNG PLAGUE. 



Man at all times and in virtue of a strong instinct theorizes on the why and the where 

 fore of everything. Valentini, in his records of the lung disease, overlooking altogether 

 many points which, with the knowledge of the present day, enable us to interpret correctly 

 the phenomena he observed, ascribed the lung plague to atmospheric agencies and unsea 

 sonable weather. Haller, a shrewd observer and great philosopher, adopted an inductive 

 system of research, and, arguing from his own sphere of observation, declared, in words 

 which deserve to be written in gold, that so far as his district was concerned the disease 

 appeared always to be imported. He did not hide the truth under a load of wild and fan 

 ciful theories in attempting to explain more than he saw and could judge of personally. 



Since the establishment of veterinary colleges in France two theories have been and 

 to a certain extent continue to be advocated. Chabert regarded the bovine pleuropneu- 

 monia so common in the dairies of Paris as contagious, whereas Huzard held the contrary 

 opinion. The field of discussion widened, and it came to be very widely admitted that 

 acute affections of the chest were contagious, and the chronic forms incapable of commu 

 nication from the sick to the healthy. Not only was this believed of pulmonary complaints 

 among cattle, it was also accepted with reference to glanders in the horse. 



Delafond, though an able advocate of the contagions character of pleuropneumonia 

 in 1844, had previously entertained grave doubts on the question. Even in his classical 

 work on the disease, while advancing a large mass of invaluable information demonstrating 

 how in truth the malady extends, his usual desire to round off and complete his works 

 led him to theorize and err as to the origin of what he calls &quot;spontaneous pleuropneumo 

 nia&quot; in cattle. This expression is not appJied by him to an ordinary attack of inflam 

 mation of the lungs, which no one ever ascribes to contagion, but to the lung plague. 

 The local or determining causes of the spontaneous form of this disease he summarizes as 

 follows : 



A. Heat and impure atmosphere of stables in which cattle live for five or six months 

 of the year, especially when this heat and impurity are combined with a very nutritive 

 aliment that produces much blood. 



B. Abundant milk secretions, required from cows in certain localities, either for the 

 sale of milk or of butter and cheese. 



C. Chills of the skin and respiration by cold, humid, misty air on pastures, either 

 during spring or autumn; the introduction of cold air in the lungs in winter on taking 

 animals from the stables to be watered. 



D. The glacial waters which cattle are compelled to drink in winter, and the unhealthy 

 waters of marshes which they have to take in summer. 



E. The hard work to which work cattle are subjected in summer in clearing for 

 ests, &c. 



F. Lastly, hereditary predisposition. 



All this classified blundering might be disposed of in one sentence, by asserting the 

 truth, that the experience of ages has shown, in many parts of the world, that all these 

 causes, singly and combined, have failed to induce a case of pleuropneumonia. Whether 

 we examine the agricultural annals of Scotland or Spain, of Canada or Texas, of South 

 America or Australia, it will be found that alternations of temperature, chills, breathing 



