116 Missouri Agricultural Report. 



work in the most efficient manner are not at present adequate; 

 but I am sure that everything needful for the best work will be 

 supplied, because of the great importance of this line of work. 



From your knowledge of the fact that hog cholera presents 

 such varied symptoms which suggest varied causes, the question 

 may arise in your minds : Will the immunizing process which we 

 have been discussing suffice for protection against these various 

 forms ? As already mentioned, it is my opinion that we have prob- 

 ably only one true -cause for the various types of epizootics affect- 

 ing the hogs of this country; but that, associated with this, the 

 hog cholera germs and the swine plague germs acting in a second- 

 ary role, give rise to some of the symptoms and lesions noted in 

 the various types of hog cholera, but it is probable that these sec- 

 ondary causes are harmless in the absence of the true cause, which 

 is found in the "filterable virus." And I think that experience 

 will prove, as our experiments indicate, that we have practically 

 only one disease to combat; and that in the method which I have 

 been describing we have an efficient means. In support of this I 

 recall your attention to the fact that the experiment pigs in lots 1 

 to 4 were exposed to the "acute haemorrhagic type" of the disease, 

 to the "slow-and-lingering" form, and to the "swine-plague" type 

 of the disease and proved resistant to them. While there is yet a 

 difference of opinion as to "swine-plague" being an independent 

 disease (and even if it should prove to be so) the losses from this 

 cause will be materially lessened because in most cases where this 

 form is noted, the hog cholera type is nearly always present; and 

 the mitigation of the disease by overcoming the "hog cholera" type 

 will doubtless lessen the force of "swine plague" with which it may 

 be associated. 



Moreover, in the preparation of the serum, the supply animal 

 is treated in a way which in fact produces in some degree a "poly- 

 valent serum" which may be effective against the secondary causes 

 mentioned. In the infected blood, which is used in the inoculation 

 of the animals to be "hyperimmunized," unfiltered blood is used. 

 It thus contains not only the "filterable virus," but also the old 

 hog cholera germs or swine plague germs with which the diseased 

 animals supplying this affected blood may be invaded. 



Another question which may arise in your minds : Is it neces- 

 sary, in order to secure a permanent immunity, to inoculate the 

 animals with diseased blood at the time they are inoculated with 

 the serum. Experiments have shown in other diseases that when 

 animals are inoculated with the protective serums alone, their im- 



