xxxii Introdiictioii. 



teresting and engrossing of any subject the human intellect can grasp 

 for examination. In the beautiful language of Hecker, ' that Omnipo- 

 tence which has called the world with all its living creatures into one 

 animated being, especially reveals himself in the desolation of great 

 pestilences. The powers of creation come into violent coUision ; the 

 sultry dryness of the atmosphere 5 the subterraneous thunders ; the 

 mist of overflowing waters, are all the harbingers of destruction. 

 ; Nature is not satisfied with the ordinary alternations of life and death, 

 < and the destroying angel waves over man and beast his flaming sword.' 

 To the general historian, the history of these plagues proves a valu- 

 able guide in determining the progress of mankind, by showing the 

 checks which have tended to retard that progress and have often pro- 

 duced marked changes in the manners and customs of a nation, in 

 peace as in war. In this history we can clearly trace the advance ot 

 human improvement. 



To the medical philosopher who desires to see his science stand on 

 the broadest basis, as well as to the lover of his species, the study of 

 ' general diseases in animals cannot fail to be of much moment. The 

 same class of causes which generate epidemic maladies are, we may 

 be certain, fertile in inducing similar diseases in the lower animals, 

 and perhaps also in plants, on which the human family so much 

 depends. For it has been a matter of common observation from the 

 earliest times, and our history will testify to its accuracy, that wide- 

 spread pestilence in plants, and murrain in animals, have frequently 

 either preceded, accompanied, or followed closely on those visitations 

 which caused mortality and mourning in the habitations of men 3 show- 

 ing an identity of causation or affinity which strongly tempts the in- 

 quirer to solve the secret of their joint production. And when it is 

 remembered that some of the animal plagvies are readily transmissible 

 to man, and often induce deadly maladies in him, there is additional 

 incitement to their study. 



To the agriculturist and political economist a knowledge of the 

 history of these alfections must always be of the most pressing import- 

 ance, as the science of comparative pathology has clearly shown that 

 many of the diseases of animals which are indigenous to our soil may 

 be deprived of their generating causes, and thus be altogether abolished. 

 Up to a recent period, the almost isolated position of Britain, witli her 

 superb flocks and herds, her matchless breeds of horses, and her fine 

 pastures, has rendered her comparatively secure against an invasion ot 

 those dread epizooties which are foreign to her shores. Since, however, 

 her ports have been opened to the importation of animals from all parts 



