386 REPORT OP THE COMMISSIONER OF AGRICULTURE. 



cesses in general. On examining the lungs of one of those hogs (Ko. 8) 

 microscopically, it was found that the serum and melted exudation, 

 which could be pressed out of the hepatized portions, still contained 

 some bacilli and bacillus germs, but no clusters (see drawing), which 

 leads me to suppose that under favorable circumstances an animal that 

 has recovered from swine plague may, after two months, be able to com- 

 municate the disease to healthy pigs. Unfortunate!}' just then no 

 healthy pig, not already designed for another purpose, was available; 

 otherwise, I would have put that question to a test. If swine plague can 

 be communicated by an animal two months after recovery — of bovine 

 pleuro-pneumonia it is well known that it can be spread by cattle that 

 have been convalescent for over two months — many, otherwise mysteri- 

 ous, outbreaks of swine-plague may be explained. 



8. THE MORBID rPvOCESS. 



Since my first report was written (December 1) numerous microscopic 

 examinations of morbid tissues, morbid products, blood, &c., have been 

 made, and bacilli siiis in different stages of development have been found 

 in every case (see drawings), but as to the manner in which the morbid 

 changes are produced nothing new has been discovered; consequently I 

 have nothing to add to what has been stated in my first report, 

 except that all my observations tend to show that most, if not all, of 

 the morbid changes — at any rate those in the lungs and in the sldn — are 

 brought about by the bacillus clusters clogging and obstructing the 

 capillary vessels. 



9. PERIOD OF INCUBATION OR STAGE OF COLONIZATION. 



Its duration seems to depend somewhat upon the.number of the bacilli 

 and baciUus germs introduced at once into the system, and also upon 

 the stage of development of those disease-producing germs at the time 

 of introduction. At any rate, the average time which elapses after an 

 inoculation before plain symptons of the plague make their appearance, 

 varies somewhat according to the quantity of infectious material inocu- 

 lated, and probably also to the resistibility of the animal organism. A 

 large quantity inoculated at once may cause a temporary reaction on 

 the second day, while a very small quantity, say one-sixth or one-eighth 

 of a drop, of pulmonal exudation does not produce any visible effect in 

 less than five to seven days. 



10. MEASURES OP PREVENTION. 



The cheapest and best way to get rid of swine plague is to stamp it out, 

 notwithstanding the disease has been allowed to exist a whole quarter 

 of a century, and has been permitted to spread over twenty-nine States 

 and Territories. A radical extermination is the only thing that will be 

 effective, unless it can be proved that a spontaneous development is tak- 

 ing place, or can take place, within the borders of the United States. 

 Fortunately, the low temperature of the winters in our principal pork- 

 producing States facilitates a stamping out, if undertaken at the proper 

 time — in the winter and in the spring — because alow temperature (frost), 

 and especially snow, interrupt very essentially the propagation of the 

 disease-germs and the spreading of the disease, and, although not 

 absolutely destroying or killing the bacilli and their germs, cause a great 

 many of them to perish or to be in a dormant state for some time. Be- 



