304 BACTERIA. 



man. Loffler himself has examined the diphtheria of a 

 calf, and he acknowledges that it is not even related to the 

 diphtheria of the human being. 



Klein considers that cats are especially susceptible to 

 diphtheria, and that they may act as the intermediate hosts 

 for the development of the diphtheria bacillus between two 

 human patients, whilst he also holds that cows may be 

 inoculated, especially on the udders, with diphtheria bacillus, 

 the disease manifesting itself in the form of small pustules. 

 He considers that milk from such cows may readily become 

 the agent by means of which the disease is spread. Eminent 

 veterinarians, however, are strongly opposed to this view, 

 and it can yet scarcely be maintained that Klein has fully 

 proved his point, although he seems to have obtained strong 

 evidence in support of his position. As he is now working 

 most carefully at the subject, however, it may be well to 

 suspend judgment until he publishes a full report of his 

 observations and experiments. 



Klein's bacilli, however, undoubtedly differ in certain 

 essential points from the bacillus described by Loffler ; most 

 important of all in the fact that whilst Loffler never suc- 

 ceeded in obtaining growths of his bacillus at the ordinary 

 temperature of the room, and was not able to grow it in 

 gelatine, those that Klein describes as occurring in the 

 pustules on the ulcerated udder of the cow grow luxuriantly 

 in gelatine at the ordinary temperature of the room. 



Klein describes a second bacillus as growing slowly upon 

 gelatine, but this he does not consider to be so important as 

 the more rapidly growing one. 



Young rabbits and guinea-pigs are the animals with 

 which most experiments have been made. It has been found 

 that rats and mice enjoy almost perfect immunity from 

 the disease, a fact which has recently been utilized by 

 Behring in connection with the production of an immunity 

 against diphtheria in rabbits and guinea-pigs. 



We shall have to wait for further light on these points, 

 but from what we have already seen, young rabbits, guinea- 

 pigs, and young dogs, may undouitedly contract diphtheria, 

 or something very similar to that disease ; both local and 

 toxic symptoms resulting from the introduction of the 

 poisonous material. It must be borne in mind that there 

 are usually several kinds of bacteria present, that the compli- 



