720 MEDICAL MYCOLOGY 



Isolated from lesions on sheep, producing copious exudates, which hold 

 the overlying wool together in hard lumps, making shearing of these areas 

 impossible and rendering much wool unmarketable ; usually attacks the younger 

 merino animals. Infection varies from 10% to 25% on some farms in Australia. 

 It is uncertain whether the similar condition, reported by Becker, is due to 

 the same organism. In the early stages, a serofibrinous fluid, with a moderate 

 number of leucocytes, exudes, is absorbed by the overlying wool, and then 

 dries. In the later stages, this exudate is mixed with a relatively large num- 

 ber of squamous epithelial cells from the surface of the skin. Chronic lesions 

 become less exudative and more keratogenous or desquamative. In the early 

 stages, the follicle is not involved (although it may be involved later), allow- 

 ing the wool to pull away from the skin. The horny layer is diffusely invaded 

 by neutrophile polymorphonuclear leucocytes. There is vesiculation of the 

 epithelium in the more superficial parts of the rete mucosum, the vesicles 

 being early invaded by polymorphs. In the cutis vera, surrounding the fol- 

 licles, there is a well-developed accumulation of leucocytes and plasma cells, 

 with an occasional polymorph. Sometimes there are areas of edema between 

 the follicles, with some hemorrhagic extravasation. The crusts consist of 

 keratinized epithelial cells and polymorphs bound together in a serofibrinous 

 exudate, along with branching mycelium. Organism pathogenic to rabbits 

 where skin has been injured by pulling out hair but not on uninjured skin. 

 Local abscesses caused on subcutaneous inoculation, lesions in rabbit and guinea 

 pigs being very close to those in sheep. Similarly pathogenic to cow and horse, 

 in the latter very desquamative. 



The hyphae are short, easily broken into arthrospores. Mycelium is also 

 present in the horny layer, and more sparsely in and around the edematous 

 portions of the corium. Branching lateral, the branches usually of smaller 

 diameter than the main trunk. Mycelium 0.5-1/* in diameter, conidia 0.5-1. 75/a, 

 arthrospores 1.8-4.5/x long, usually 3.6/a, often thickened at one end with a 

 wavy contour. Gram-positive, not acid-fast. Aerobic, growth in agar shake 

 at all depths, but the organism is not a strict anaerobe. Optimum tempera- 

 ture 37°, growth very poor at 22° C. 



On peptone agar, growth in 24 hours at 37° even, raised, convex to pul- 

 vinate, yellowish, opaque, somewhat glistening, 1 mm. in diameter. After 48 

 hours colony more irregular, less raised, more tenacious, not spreading. No 

 aerial hyphae. Color better developed at 22°, antimony yellow (Ridgway 

 16 'b), medium not colored, colonies flatter, center umbonate with raised 

 lobate or lobulate margins. Deep blood agar plates show clear zone of hemol- 

 ysis, 3.5/x in diameter, around colonies. No digestion in Loeffler's blood serum, 

 good growth, more tenacious. Gelatin liquefied only at pH 7.6, growth sac- 

 cate, 1 cm. in 14 days. At 37° C. liquefaction is complete in 9 days. No visible 

 growth on potato. In peptone broth, pellicle appears in 24 hours, no clouding, 

 growth on sides of tube with slight sediment, which becomes more abundant as 

 pellicle falls, becoming mucoid. Litmus milk bleached in 4 days, medium 

 digested in 7-8 days, medium yellow. Bromcresol purple milk digested in 



