140 THE ACUTE SELF-LIMITED INFECTIONS 



Animals do not contract cholera either spontaneously 

 or artificially, but they may be killed by the germs or 

 their poisons. The active acquired immunity they get 

 by repeated injections has been described. It has not 

 been found practical to obtain any serum from animals 

 which can be injected into human beings as a treat- 

 ment. Dead spirilla, however, can be injected into 

 well persons as a protective measure, precisely as is 

 done for typhoid and plague, and with good results. 



BACILLUS DYSENTERIC. 



Dysentery occurs in two forms the bacillary type 

 and the amebic type. The former is caused by bacteria, 

 while the latter is a protozoon disease (see Chapter 

 XIV). Bacillary dysentery is an acute infectious 

 disease, its chief lesion being a violent inflammation 

 of the lining of the large intestines. 'The disease is 

 caused by the Bacillus dysenteries or dysentery bacillus. 

 It is, however, better to say that a group of organisms 

 under this name gives rise to it because there are many 

 varieties with different chemical and serum reactions, 

 producing attacks of varying severity. Their general 

 pathogenic and etiological effects may be discussed 

 together, however. The usual ileocolitis of children 

 is not due to the dysentery bacillus, but some mem- 

 bers of the dysentery group have been found respon- 

 sible for small epidemics of diarrhea among children. 



In cholera the chief lesions are in the lower small 

 intestine, but otherwise the two diseases have many 

 things in common. 



The bacilli enter probably only by the mouth in 



