400 ACTINOMYCETES. 



these experiments an increase of the bacteria occurs almost 

 exclusively locally, and only rarely can they be cultivated 

 from the internal organs. 



Subchronic and chronic cases (death sometimes occur- 

 ring only after months) present changes in the internal 

 organs which are less marked, or no alterations at all are 

 found. At the point of injection all changes may be lack- 

 ing or ulcers may follow necrosis of the skin. The animals 

 are always emaciated and very much reduced in weight. 

 Escherich never saw postdiphtheritic paralysis in experi- 

 mental animals; other authors have occasionally. 



Rabbits are much more resistant to subcutaneous inocu- 

 lation than guinea-pigs; white mice and rats are almost 

 immune. On the contrary, cats, dogs, and cows are sus- 

 ceptible. Of birds, young pigeons and small birds 

 (finch, siskin, etc.) are especially susceptible; hens less, 

 and only when young. 



Diphtheritic diseases of mucous membranes analogous 

 to those observed in human diphtheria may be produced 

 by rubbing diphtheria bacilli into the slightly injured (not 

 the uninjured) mucous membrane of the trachea and con- 

 junctiva of rabbits, of the throat of monkeys, of the 

 throat and larynx of pigeons and hens. The disease pro- 

 cess and membrane formation remains local. The best 

 results follow inoculations upon the vaginal mucous mem- 

 brane of guinea-pigs (Loffler): If one pulls apart the 

 vagina, which is always feebly adherent, and places a pin- 

 head-sized quantity of diphtheria bacilli upon the mucous 

 membrane, which has always received a minimal injury 

 in the manipulation of separation, on the following day 

 there is marked redness and hyperemia, and after forty- 

 eight hours the formation of a thin, closely adherent cover- 

 ing can be demonstrated. This infection may terminate 

 in recovery or death. 



Roger and Bayeux produced, by the injection of J to 1 

 drop of diphtheria poison into the trachea of rabbits, beau- 

 tiful diphtheritic membranes, while guinea-pigs die too 

 soon for it to appear. 



(6) In man there have been no experiments. 



Immunization. — Animals may be immunized against 

 diphtheria bacilli: 



