KEPOET OF THE SECEETARY. 169 



eations culminated in 1903 in the discovery that this fatal disease is 

 caused by a microorganism of such minute size that even the most 

 powerful microscopes do not enable us to determine its form or 

 structure. This discovery of the true cause of hog cholera . enabled 

 the department's investigators to attack the problem of prevention 

 with intelligence and with some prospect of success. 



Following the discovery of the true cause of hog cholera, the bureau 

 succeeded in producing a protective serum from immune hogs which 

 serves to prevent an attack of hog cholera in animals which would 

 certainly succumb except for the serum inoculation. This antihog- 

 cholera serum has been patented and assigned to the free use of the 

 people of the United States. It has been found that this serum can 

 be produced at a cost sufficiently low to warrant its employment in 

 practice. 



The department, through bulletins and other special notices, has 

 advised all the States of the Union of this discovery and has urged 

 them to undertake the manufacture of this serum for the benefit of 

 farmers. At the present time 28 States have done more or less 

 work along this line, and more than 1,000,000 hogs have been given 

 the protective inoculation with most satisfactory results. 



In order to understand what the discovery of this serum may mean 

 to the people of this country, we need merely to consider that the 

 value of property in swine in the United States exceeds $500,000,000, 

 and that a conservative estimate shows that the average yearly loss 

 from hog cholera must amount to more than $18,000,000. 



The investigations of the department have thus placed the people 

 of the country in a position to save all, or a greater part, of this 

 loss and, furthermore, as the serum may be used to prevent hog 

 cholera, farmers should soon be in a position to raise greatly in- 

 creased numbers of hogs without being deterred, as .they are now, 

 by the fear of this destructive disease. 



GLANDEUS AND OTHER DISEASES. 



The diagnosis of glanders, Malta fever, dourine, and infectious 

 abortion by the application of complement-fixation tests to the blood 

 serum is one of the recent achievements that has a far-reaching im- 

 portance. By this method it is now possible to diagnose these dis- 

 eases accurately and promptly. This is a gi-eat improvement over 

 the uncertainty of former methods. About 2,500 complement-fixa- 

 tion tests were made during the past year. 



Infectious abortion is a scourge of the cattle industry at the 

 present day, and has been a subject of special investigation during 

 the past two yeare. With prevention in view very extensive experi- 

 ments have been made for the purpose of discovering some effective 



