2I02 



TROPICA L DERMA TOM YCO SES 



recently on the subject, very different clinical descriptions having 

 been given and the condition being ascribed to widely different 

 germs. 



Paxton, Wilson, Pick, and later Payne, Patterson, Crocker, 

 Pusey, etc., described the hairs as presenting irregularly lobed 

 masses of hard consistency in which were often embedded some of 

 the fibres of the cortex. 



According to Crocker, the fibres of the whole shaft may be split 

 up and the hair may break off with a brush-like termination. The 

 researches on the aetiology by various authorities gave the most 

 widely different results, various bacilli being described by Payne and 

 Patterson, a diplococcus by Eisner and later Sonnenberg, and a 

 micrococcus by Colombini, etc. Babes, Pick, Balzer, and Bar- 

 themly considered that the Bacillus prodigiosus played a role in the 

 causation of the affection. 



In 191 1 Castellani carried out an investigation in the tropics, 

 describing the condition as seen there and differentiating three 

 varieties — the yellow variety, the black variety, the red variety. 

 He demonstrated that the yellow variety was caused by a nocardia 

 (Nocardia or Cohnistreptothrix tenuis Castellani) ; the black variety 

 by the same nocardia plus a black pigment producing coccus 

 {Nigrococcus nigrescens CasteMni) living in symbiosis with it; the 

 red variety by the same nocardia plus a red pigment producing coccus 

 living in symbiosis with it, and which was later on called Rhodococcus 

 castellanii by Chalmers and O'Farrell. Castellani's work was 

 confirmed and amplified inthe Sudan by Chalmers and O'Farrell, who 

 suggested for the affection the term ' trichonocardiasis ' ; in West 

 Africa by Macfie, who described a variety of the -red type: fusca ; 

 and by various observers in several other countries. In 1915-1918 

 Castellani observed in the Balcanic-Adriatic Zone the three varieties 

 he had described in the tropics, and found the same organisms. 



iSItiology. — The researches of Castellani have demonstrated that 

 the yeUow variety is due to a very thin, bacillary-like fungus, for 

 which he proposed the name Nocardia tenuis, later changed into 

 Cohnistreptothrix tenuis. The black and red varieties are due to a 

 symbiosis of this fungus with chromogenic cocci, a coccus producing 

 black pigment in the black variety, a coccus producing a red pigment 

 in the red type. 



Nocardia tenuis Castellani, 191 2 [Cohnistreptothrix tenuis Castellani, 1912).- — 

 The microscopic examination of the nodules reveals the presence of enormous 

 numbers of bacillary-like bodies, which are Gram-positive, but not acid-fast. 

 If the nodules are kept in alcohol or formalin for several months, the fungus 

 apparently loses partially or totally its property of being stainable by Gram's 

 method. They vary in length, 4 to 10 ^ and more; the average breadth is 

 approximately 0-3 to o-6 /j,; they may be straight or variously bent, occasion- 

 ally branching; they are fairly closely packed together, and are embedded 

 in an amorphous cementing substance. In regard to cultivation, Chalmers 

 and O'Farrell observed some slight growth in hanging drops of equal parts 

 of human serum and normal sahne. Macfie in one case succeeded in cultivating 

 the fungus on ascitic agar, the colonies being very small and translucent. 



