THE TRICHOMYCETES 157 



involution forms, perhaps produced by resistance of the 

 tissues. The filaments are sometimes ' acid-fast.' 



When pus, sections, or teased-up specimens from human 

 sources are stained by Gram's method, the filaments and 

 gonidia are Gram-positive, while the clubs situated around 

 the periphery and showing a radiating structure do not 

 usually stain Jby Gram's method. Carbol-fuchsin and 

 picric acid may be used, when the fungus stains red and 

 the tissue yellow. In the bovine organism the clubs 

 stain well by Gram and are well marked, clubs of the 

 hominis variety being stunted. The prominent central 

 filamentous network of the hominis variety is generally 

 replaced by a mass of debris in the bovine type. 



Cultural Characters. In artificial media clubs are not 

 found. The organism grows well, and for almost an 

 unlimited time, on glycerin-agar and potato. Fully 

 developed cultures on potato are peculiar and character- 

 istic: a dull raised and wrinkled growth, of considerable 

 thickness, of a bright sulphur-yellow or light chocolate 

 colour, somewhat similar to the lichen commonly seen 

 on apple-trees. 



Occurrence and Distribution. Actinomyces grows on 

 grasses and cereals, particularly on barley, and especially 

 on damp rich soils. Infection is due to the piercing of 

 a mucous surface by a portion of a cereal bearing the 

 fungus; possibly the fungus may also gain access to the 

 system by inspiration. 



It does not seem likely that cattle are infected by 

 contact, and although some human cases have occurred 

 after eating grains of barley, Wright is of opinion that 

 actinomyces is normally present in the mouth, and that 

 irritation caused by the foreign particle merely facilitates 

 invasion of the tissues. The change of teeth in young 

 animals is regarded as a period when risk of infection is 

 greatest. Scirrhous cord, the fibrous tumour found on 

 the end of the spermatic cord of the ox, is stated by 

 Stockman to be caused by the entrance of the actinomyces 

 by the wound of castration. 



Pathogenesis. Cattle are the principal subjects of 

 the disease, but it also occurs in pigs, sheep, horses, 

 squirrels, and man. In animals the disease is usually 

 local and may arise in various parts of the body, the 

 head and neck, particularly the tongue, being most 



