PRINCIPLES OP MEAT PRESERVATION. 125 



must vanquish and leave an impress on the annals of discovery 

 which time cannot efface. From the earliest days when I 

 studied physiology in London it appeared to me that the theory 

 of spontaneous generation would soon find its resting-place in 

 oblivion. At that time nothing could be more unsatisfactory 

 than the state of knowledge regarding the origin of many para- 

 sites and the development of contagious diseases. But these 

 subjects engrossed my attention when engaged in a prolonged 

 continental tour, visiting medical and veterinary institutions. 

 Kiichenmeister, Van Beneden, Von Siebold, Haubner, Leuciiart, 

 Esebricht, Ercolani, Baillet, and numerous others, were then, and 

 have since been, at work explaining the strange metamorphoses 

 which invest the lives of entozoa. The opposition which retards 

 the dissemination of truth was rarely better illustrated than by 

 the manner in which demonstrations of the methods of transmis- 

 sion of parasites were received by farmers, and even veterina- 

 rians, in Scotland. Dogs were artificially infested with tape- 

 worms, and these were transmitted to sheep, which soon showed 

 symptoms of cerebral torment from the growing bladder-worms, 

 no doubt often probing the sensorium with their erectile heads. 

 Many of the canny Scots reputed me insane and an enthusiast. 

 They thought worse still of me when I insisted on the dangers 

 and irretrievable losses incurred by a traffic in diseased animals 

 alive and dead. But my efforts as a veterinary teacher were 

 from the commencement directed to the complete overthrow 

 of old-established doctrines and practice in relation to cattle 

 plagues ; and although, even at the present day, few of the most 

 advanced European veterinarians venture as far as I have done, 

 I know that the most careful experiments and observations will 

 complete the demonstration of a truth which bears an intimate 

 relation to the subject of this lecture. Epizootics of contagious 

 nature exist which are transmitted through time and space by 

 reproduction of a contagium or virus, and are incapable of 

 spontaneous development. This class of diseases is well de- 

 fined, and the protection of farm-stock from their ravages rests 

 on the complete understanding of that simple law. It is as 

 impossible to have the spontaneous development of a case of 

 lung plague, rinderpest, foot and mouth disease, hydrophobia 

 or smallpox, as it is to have a man born out of nothing ; and it 

 was the enunciation of such a doctrine that led the " London 



