THE LUNG PLAGUE. ' 31 



he observed, ascribed tlie lung plague to atmospliericag-encies and unsea- 

 sonable weath'^r. Mailer, 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 Avild 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 pleuro-pneumoniaso common in the dairies of Paris 

 as contagious, whereas Huzard held the contrary opinion. The Held 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 communication from the sick to the healthy. Kot only was this 

 believed of pulmonary complaint among cattle ; it was also accepted 

 with reference to glanders in the horse. 



Delafond, though an able advocate of the contagious character of pleuro- 

 pneumonia iu 1844, had previously entertained grave doubts on the ques- 

 tion. Even in his classical work on the disease, while advancing a large 

 mass of invaluable information demonstrating how in truth the nmlady 

 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 ^^spontaneous pleuro- 

 pneumonia^^ in cattle. This expression is not applied by him to an ordi- 

 nary attack of inflammation 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, this 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 pas- 

 tures, either during spring or autumn ; the introduction of cold air in the 

 lunas 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 w^hich work cattle are subjected in summer in 

 clearing forests, &Q,. 



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 agricul- 

 tural annals of Scotland or Spain, of Canada or Texas, of South America 

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



