118 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



to the test, whereas of 360 positive sera, 290 (80.5 per cent) were 

 positive. Furthermore, of the affected animals 81 (25.8 per cent) 

 gave only slight positive reactions, and 80 were atypical. The grand 

 total of 81.6 per cent of accurate reactions obtained is by no means 

 sufficient to make the test practicable for the control of the disease, 

 especially since the allergic tests which we have at our command are 

 more reliable. No satisfactory explanation can be given as to the 

 failure of reactions in known tuberculous infections or for the positive 

 reactions in apparently healthy individuals. There exists a possi- 

 bility, however, that some of the positive reactions in the negative 

 cases may have been due to a previous tuberculinization of the cattle, 

 since the histories of the animals furnishing the sera were not avail- 

 able. 



BLACKLEG VACCINE. 



During the fiscal year 5,436,221 doses of blackleg vaccine were dis- 

 tributed by the bureau, an increase of nearly 2,000,000 doses over the 

 preceding year. A concrete building has been provided at the 

 experiment station for handling the calves from which the virus is 

 obtained. This adds materially to the facilities for preparing the 

 vaccine. 



SUPERVISION OF BIOLOGICAL PRODUCTS. 



In the enforcement of the virus-serum-toxin law of 1913 the patho- 

 logical division has continued to exercise supervision over the prepa- 

 ration of biological products, with the exception of anti-hog-cholera 

 serum, hog-cholera virus, tuberculin, and mallein, the work regarding 

 which has been conducted by the Biochemic Division. The supervi- 

 sion of the Pathological Division has covered 154 products made by 

 22 firms and 17 products imported by 2 firms. An annual inspec- 

 tion is made of the laboratories and the methods employed in pre- 

 paring and testing these products. Suggestions have been made 

 to the various firms regarding methods for securing greater accuracy 

 in identifying cultures, methods of testing products for sterility, and 

 keeping laboratory records. 



From time to time samples of the various biological products 

 manufactured by firms throughout the country are purchased in the 

 open market, and systematic tests are made for sterility, potency, 

 etc. Most of the specimens examined during the past year proved 

 satisfactory. However, in several instances such defects as con- 

 taminations, vaccines possessing too great a degree of virulence, etc., 

 were detected. In such cases the matter was taken up with the manu- 

 facturers and steps were taken to prevent recurrences. 



AUTOPSIES ON ANIMALS FROM THE NATIONAL ZOOLOGICAL PARK. 



Autopsies were made on 115 wild animals from the National 

 Zoological Park. More than 50 per cent of the deaths were due to 

 diseases of the digestive and respiratory tracts. In birds the former 

 system is most often attacked, while in mammals it is the latter. Of 

 the infectious diseases tuberculosis plays the most important role, 

 there being 8 cases in birds and 4 in mammals. Aspergillosis of the 

 lungs and air sacs was found in 5 birds. 



