ORGANISMS WHICH PRODUCE DISEASE 69 



cord-like and knot-like swellings, called by veterinary surgeons 

 " farcy-pipes " and " farcy-buds." These are liable to a cheese- 

 like form of necrosis called caseation, and may break down, 

 ulcerate, and discharge purulent lymph containing the organism. 

 Similar nodules "glanders-" or " farcy -tuber cles " may be 

 produced in the lungs, and are firm and more or less fibrous, 

 with a tendency to caseation and softening. 



In man, the infection, which usually attacks those who have 

 charge of and are in contact with horses, may also follow an 

 acute or a chronic course. Inoculation may occur in the nose 

 from breathing air contaminated by the sneezing of an infected 

 animal, or on the hands or face through a wound. The chronic 

 form resembles the farcy of horses, and spreads especially along 

 the lymphatics. The acute form in man is a very serious and 

 often rapidly fatal disease, resembling pyaemia, with a multiple 

 pustular eruption, especially on the face and arms, resembling 

 confluent smallpox, together with intense fever and multiple 

 abscesses in the skin, muscles, lungs, and other organs. 

 Laboratory workers have sometimes fallen victims to this 

 disease whilst investigating the condition. 



Microscopically, B. mallei is a small, slender, rod-shaped 

 bacillus, often very slightly curved. It is non-motile, Gram- 

 negative, rather difficult to stain with ordinary dyes, and does 

 not form spores. It is easily cultivated, and grows best on 

 glycerinated potato, upon which it gives a characteristic pale 

 brown, syrupy, or honey-like growth. It is easily killed by 

 heat and antiseptics. 



Diagnosis of the disease in horses in pre-bacteriological days 

 used to be made by putting along with the suspected animal 

 a donkey, which is very liable to the acuter forms of the 

 disease. Now, diagnosis is made by the bacteriological ex- 

 amination of the discharge, by the inoculation of a guinea-pig, 

 and by the mallein and other serological tests. The mallein 

 test, which consists of the injection of a concentrated glycerin- 

 broth culture prepared in a similar manner to tuberculin (see 

 p. 81), produces in an animal suffering from the disease a febrile 

 reaction and marked local pain and swelling. 



Vibrio cholerae. Cholera, the specific infective disease pro- 

 duced by this organism, is characterised by intense diarrhoea 

 and general toxic symptoms such as muscular cramps, heart- 

 weakness, and emaciation. The infection is usually carried by 

 drinking water contaminated by infective excrement from the 

 bowels, and by the eating of raw vegetables, salads, and other 

 foods similarly contaminated, or which have been washed in 

 infected water. Flies may carry the infection after alighting 



