GENERAL CHARACTERS OF SPIROCILETES. 63 



lesion, followed by a generalised infection. Relapses 

 do not occur as a notable feature, and enlargement of 

 the spleen is also inconstant. The causality of the 

 spirochsetes present is not yet absolutely proved. 



In a third group, in which we may place Vincent's 

 angina, ulcerative granuloma of the pudenda, and per- 

 haps the disease recorded by Dodd in the pig, there is 

 merely a local affection of the skin or of mucous mem- 

 brane, conveyed in the last two cases by direct contact. 



The three classes may be considered to constitute a 

 descending scale of virulence on the part of the para- 

 sites, a local lesion being caused when the degree of 

 virulence is slight, a local lesion with subsequent gen- 

 eralisation when it is rather greater, and an immediate 

 septicaemia when it is most intense. Cases of congenital 

 syphilis in which death occurs, but no anatomical 

 lesions are discovered, have been attributed to a septi- 

 csemic action of the Sp. pallida. 



METHODS OF STAINING. 



The larger spirochaetes may be stained by the ordi- 

 nary methods used for protozoa haematoxylin (Dela- 

 field's or Heidenhain's), Giemsa's stain, etc. They are 

 not stained by carmine thus resembling bacteria 

 rather than protozoa. 



For the smaller spirochaetes, especially for Sp. pal- 

 lida, a large number of methods have been recom- 

 mended. 



Giemsa's Stain. This is made as follows: Azur II 

 eosin 3 grm., azur II 0.8 grm., pure glycerine 250 grm., 

 methyl alcohol 250 grm. One drop of this solution is 

 added to i c.c. of distilled water. Stain for ten to fifteen 

 minutes (see Plate, Fig. A) . 



Schereshewsky recommends diluting 13 to 15 drops of 

 this solution with 10 c.c. of 0.5 per cent, solution of 



