82 BACTERIOLOGY 



ally of the skin. When the nerves are invaded, patches of 

 anaesthesia and loss of the normal pigment of the skin occur, 

 the latter phenomenon giving rise to the description, " a leper 

 white as snow." The method of infection, which is not yet 

 fully understood, may be perhaps direct from individual to 

 individual, or it may be transmitted by parasites such as the 

 louse. 



The bacillus in its acid-proof stage is very like the tubercle 

 bacillus, though usually a little thicker. It has only recently 

 been successfully cultivated, and has been found to be pleo- 

 morphic, i.e. found in different forms, four such forms being 

 now described, viz. (1) acid-proof bacillus, (2) non-acid-proof 

 bacillus resembling a " diphtheroid'' organism (see p. 67), 

 (3) an acid-proof and (4) a non-acid-proof Streptothrix (see 

 p. 15). Treatment with vaccines has met with some success, 

 the reactions obtained proving the specific nature' of the 

 organisms cultivated. 



The Pathogenic Trichomycetes 



The Trichomycetes or Filamentous Higher Bacteria are 

 more or less intermediate in position between the Lower 

 Bacteria and the Higher or True Fungi such as the Moulds and 

 Mildews. The most important disease-producing members of 

 this group are branching organisms which for convenience, 

 though perhaps not with scientific accuracy, may be classed 

 together as the Streptothriceae. 



Streptothrix actinomyces, the cause of Actinomycosis, may 

 be taken as the most important member of this group, though 

 disease in man may also be produced by certain other closely- 

 allied organisms, e.g. one form of Madura foot or Mycetoma 

 by Streptothrix madurae, and a variety of Pyaemia by 

 Streptothrix (or Cladothrix) asteroides. Actinomycosis is 

 especially a disease of cattle in which it causes the charac- 

 teristic conditions known as "Woody Tongue," "Lumpy 

 Jaw," etc. : and when communicated to man there is a tendency 

 to the breaking down of the lesions, with chronic abscess- 

 formation or ulceration, and the discharge of pus containing 

 yellowish or greenish granules which contain, and are largely 

 composed of, the organism. Infection usually occurs through 

 the mucous membrane of the mouth, pharynx, oesophagus or 

 intestine, the neighbouring tissues becoming invaded, usually 

 with abscess-formation. In some cases the air-passages and 

 lungs are the site of infection. Generalised infection may 

 occur by the blood-vessels, with widespread secondary lesions 

 in the liver, lungs, brain, or bones. 



