and Laboratory Methods. -2087 



species. In virtue of these conditions and possibly other undetermined condi- 

 tions, the udder, so to speak, exerts a selective action upon the bacteria which 

 may be temporarily present in it. In this, they are of course aided by the 

 mechanical expulsion of bacteria in the process of milking. 



In order to throw a little light upon this problem, experiments were conducted 

 in inoculating udders with well-marked but harmless bacteria which could be 

 easily recognized by their cultural characteristics. Bacillus prodigiosus and B. 

 exiguum (IX), both of which are marked by their pigment production, were the 

 ones experimented with. Cultures of these were smeared upon the ends of the 

 teats, so that the bacteria might work their way up into the udder, just as any 

 other germ might which comes in contact with the ducts of the teat. In the case 

 of B. prodigiosus about 20,000 per c. c. were present in the fore milk at the first 

 milking 8 hours after inoculation. By the third milking, only a few were present, 

 and after that it disappeared completely. The experiment was repeated with 

 B. exiguum with similar results, although a smaller number, 240 per c. c, were 

 present in the first milking, and by the fourth milking it had disappeared. No 

 doubt the small number was due to the fact that this germ grows much more 

 slowly than B. prodigiosus as will be seen by reference to the description (see IX). 



In view of Ward's discovery of B. fiuorescens liquefacieiis in the udders of 

 certain cows, it seemed advisable to attempt to colonize this germ in the udder, 

 and a bouillon culture was smeared upon the ends of the teats of a cow in the 

 manner already described. This bacillus was recovered in the foremilk six hours 

 after the teats were smeared, but was not found in the fore milk of the second 

 and third milkings. 



It does not seem probable that an aerobic bacterium of this character is able 

 to live and compete with falcultative anaerobic bacilli. Further, the optimum 

 temperature for the fluorescing bacterium is not 37°. 



Possibly, by continuous experimentation, we might have finally discovered a 

 species which would persist in the udder, but, at the same time, the bacteria 

 chosen have evidently fared much" the same as other more or less injurious forms 

 which may occasionally find temporary lodgment in the udder. Exception, how- 

 ever, may occur, as we have the gas and taint producing bacillus located by 

 Ward and Moore in the udders of the cows of a particular herd. 



Another fact that may have a bearing on this problem is that normal healthy 

 organs, taken from the body immediately after death, may contain bacteria which 

 are capable of development. Thus, Ford (XX) has shown that 80 per cent, of 

 healthy organs, removed from killed guinea pigs, rabbits, dogs and cats, con- 

 tained living bacteria. No udder tissue was examined by him, and in order to 

 ascertain if bacteria existed in the udder of healthy animals, a few experiments 

 were made along these lines, but they are open to criticism, because it is impos- 

 sible to say with any certainty that the bacteria found came from the. animal's 

 glands or blood, or from infection through the teat. However, by selection of 

 cows which had been dry for several weeks before slaughter, the latter objection 

 is to some extent overcome. The liver was examined at the same time, and its 

 bacterial content, if any, noted. F. C. Harrison, 



Ontario Agricultural College. M. CuMMING. 



