668 THE PARASITIC HYPOMYCETES 



Culture media. Broth. Whitish irregular flakes appear, some of which 

 float on the surface and form a greyish dusty pellicle while others fall to the 

 bottom. The medium remains clear. 



Glycerin-broth. A similar but more luxuriant growth. 



Agar. Small, rounded, raised, opaque, yellowish-white colonies develop, 

 which coalesce to form a mammillated, folded, dull, dusty-looking culture. 



Serum. The growth has the same characteristics as on agar but is less 

 abundant. 



Potato. An abundant growth develops consisting of considerably raised, 

 dry, scaly, yellowish plaques with sharp cut edges. 



Milk. The growth assumes the form of small greyish granules. The 

 medium is not coagulated. 



XIV. DISCOMYCES CAPR^l (Gedoelst). 



Syn. Streptothrix caprce Silberschmidt. 



This parasite was found in the lung of a goat affected with pseudo- 

 tuberculosis. 



1. Experimental inoculation. 



Cultures of Discomyces caprce are virulent for rabbits and guinea-pigs : 

 white mice are susceptible but to a lesser degree. 



Sub-cutaneous inoculation into rabbits and guinea-pigs leads to the forma- 

 tion of an abscess ; inoculated intra-venously the parasite produces tubercles 

 in the internal organs. " On histological examination these tubercles show 

 a structure similar to that of true tubercles due to the tubercle bacillus. 

 Giant cells are found in the lungs. The tubercles rapidly caseate " (Silber- 

 schmidt). 



2. Morphology. 



(a) Microscopical appearance. The mycelium consists of very fine, more 

 or less branched filaments of varying length. In the tissues the longer forms 

 predominate : in agar cultures, on the other hand, and in colonies growing 

 on the surface of broth, short rod-shaped forms are the most noticeable 

 feature. 



Discomyces caprce is non-motile : in cultures it forms elongated spores 

 which are readily decolourized and are only slightly resistant to heat. 



Staining reactions. Discomyces caprce stains with the basic dyes con- 

 taining a mordant : it is gram-positive. In the tissues the organism is more 

 difficult to stain than in cultures : use Gram's stain with eosin as a counter- 

 stain. 



(/?) Cultural characteristics. Discomyces caprce is almost strictly aerobic. 

 It grows at ordinary temperatures (but best at 33-37 C.) on the ordinary 

 culture media, but particularly well on 2 per cent, glucose broth and on 

 potato. 



Culture media. Gelatin. Gelatin is not liquefied. In plate culture, the 

 colonies develop slowly and resemble small colonies of moulds. In stab 

 culture, discrete flocculent colonies develop in the depth of the medium, 

 while on the surface the growth takes the form of a dry brownish layer. 



Glycerin-agar. A dry brownish layer appears, subsequently sprinkled 

 with white. The culture grows into the agar in the form of fine radiating 

 prolongations. Occasionally the colonies have a crater-like depression in the 

 centre. 



Broth. Sugar broth is better than ordinary broth. Growth is visible after 

 about 48 hours in the warm incubator (37 C.) ; the medium is clear ; small 



