314 TEXT-BOOK OF BACTERIOLOGY. 



By removing a trace and starting a pure culture on agar, it will 

 be perceived that the development, in the beginning, keeps within 

 narrow limits. The medium evidently does not agree with the 

 bacteria; the growth remains restricted to the immediate neighbor- 

 hood of the inoculating line, and the film (of a whitish lustre) ex- 

 tends bub very slowly. But on transferring the colony from 

 the first generation to the second, we will at once notice that the 

 bacteria quickly accustom themselves to the originally unsuitable 

 culture medium; the colonies proliferate more and more, and finally 

 spread over the entire surface. 



A thick, whitish, opaque coating arises on blood- serum; the 

 same is the case with a serum suggested by Loffler for breeding 

 diphtheria bacilli. This serum consists of 3 parts of cattle-serum 

 and 1 part of bouillon containing 1^ of peptone, 0.5^ of sodium 

 chloride, and 1^ of dextrin. 



In bouillon, at breeding temperature, the bacilli form white, 

 very small, firmly cohering, peculiarly gritty grains which quickly 

 sink to the bottom or adhere to the walls of the tube, while the 

 fluid itself remains clear, so that the appearance of such cultures is 

 usually quite characteristic. The diphtheria bacilli develop like- 

 wise very readily in sterilized milk. 



In experimental transmission, we must never overlook the fact 

 that animals under natural conditions are never attacked by hu- 

 man diphtheria, and hence but little adapted for our purpose. All 

 the affections running a similar course (such as the diphtheria of 

 calves, pigeons, and chickens) are originally altogether different 

 diseases and arise from other causes. 



Inoculations with diphtheria bacilli have, however, been rather 

 successful in spite of these unfavorable preliminary conditions and 

 Loffler obtained some very important results. He found that mice 

 and rats were very refractory, while rabbits and Guinea-pigs, and 

 most of the birds, such as finches, sparrows, and especially pigeons 

 and chickens, are always accessible to the influence of the bacilli. 



After injecting Guinea-pigs subcutaneously, purely local changes 

 first develop at the point of infection. Grayish-white pseudo- 

 membranous masses are formed. More general disturbances soon 

 appear; an extensive hemorrhagic oedema in the subcutaneous 

 cellular tissue usually-arises all around the point of inoculation. 

 This may be followed by effusions into the pleural cavities and 

 lobular consolidation of the lungs. The bacilli also produce pseudo- 

 membranes whenever introduced into the opened trachea of 

 rabbits, chickens, and pigeons; also on the superficially injured con- 

 junctiva of rabbits and the lacerated introitus vaginte of Guinea- 



