BUREAU OF ANIMAL INDUSTRY. 255 



An experiment relative to the derivation of a healthy from a tuber- 

 culous herd of cattle is still in progress. 



Considerable work has been done with a bacterium which, as far 

 as we are able to determine, has not been described before. The germ 

 is of common occurrence in the samples of commercial milk examined 

 at the station, and there are several cows at the station which secrete 

 it with their milk. It was found to be present in the milk of approxi- 

 mately 10 per cent of a herd of about 150 dairy cows located in the 

 District of Columbia. It reaches the milk of apparently healthy cows 

 before the milk leaves their udders, and it causes in guinea pigs a 

 serious chronic disease, at times closely resembling tuberculosis in its 

 gross pathologic appearance. Tlitis bacterium, from our present 

 viewpoint, seems to have been overlooked in the past because it does 

 not grow on ordinary culture media and because it is very chronic in 

 its pathogenic action on guinea pigs, wliich animals it affects both 

 through inoculation and ingestion. It is a very minute. Gram-posi- 

 tive, nonacid-fast bacillus. We have cultivated it artificially and 

 have not only proven that pure cultures produce its characteristic 

 pathologic lesions in guinea pigs, but have recovered it from the tis- 

 sues of guinea pigs infected with pure cultures. 



Two conditions evidently due to the bacillus are specially note- 

 worthy. One is that it occasionally causes paralj^sis in guinea pigs, 

 and the other that it at times causes a pecidiar disease in or about the 

 bone articulations. Neither the paralysis nor the disease of the 

 articulations has been observed in any of the large number of guinea 

 pigs at the station which have not been infected with the bacillus. 

 The joint disease is particularly interesting because bacteriologically 

 it is associated with a micrococcus, thus foreshadowing the possibility 

 of a microorganism which by itself may be harmless but wliich in the 

 presence of another microorganism may cause disease of the bones or 

 their articulations. The importance of tliis bacterium remams an 

 unsolved question wliich will receive careful attention in the future. 

 Just at present it is important because it proves conclusively that 

 germs, pathogenic for guinea pigs and possibly for other animals, derived 

 directly from the udders of milk cows, which no system of inspection 

 applied to dairy herds, barns, milk utensils, etc., can eliminate, and 

 which an ordinary bacteriological examination of milk would fail to 

 detect, are of fairly common occurrence in milk. The thermal death 

 point of the bacillus is 60° C. (140° F.) maintained 15 minutes. 



OTHER WORK. 



During the fiscal year facilities were provided at the Experiment 

 Station for the various divisii^ns of the bureau to aid them in their 

 investigations concerning tetanus, Johne's disease, glanders, swamp 

 fever, dourine, blackleg, infectious abortion, lip-and-leg ulceration, 

 sarcoma, hog cholera, caseous lymphadenitis, ringworm, rabies, 

 diamond skin disease, bighead of sheep, Texas fever and cattle ticks, 

 intestinal parasites of sheep, gid, dips for removing external para- 

 sites, inbreeding, studies in Mendelian laws of inheritance, selective 

 breeding, the possible elfects of inbreeding on susceptibility of dis- 

 ease, etc. 



