280 DR BENNETT ON THE PARASITIC VEGETABLE STRUCTURES 



In several other cases which have come under my observation, I have satis- 

 fied myself that the formation of pustules is not essential to the disease, although 

 they are often present. Hence the mistake of those pathologists who classified 

 Porrigo lupinosa amongst the Pustulse. M. GRUBY says that pustules are never 

 present, which is equally erroneous, although they appear to be a secondary re- 

 sult, attributable to the irritation the disease produces in some individuals. On 

 the other hand, I have never seen the disease produced without having been pre- 

 ceded by desquamation of the cuticle, an observation which appears to me of some 

 importance, inasmuch as, if true, the disease ought to be classed amongst the 

 Squamce. 



According to M. GRUBY, the plants grow in the substance of the epidermis. I 

 have made observations to determine the correctness of this statement, and found 

 that the whole inferior surface of the capsule is formed of epidermic scales, thickly 

 matted together. These are lined by an amorphous, finely granulated matter, from 

 which the plants appear to spring, and which unites the branches and sporules to- 

 gether en masse. Superiorly, however, the epidermic scales are not so dense ; and I 

 have always found them more or less broken up, and not continuous. The observa- 

 tions just described are here valuable, as indicating the probable mode in which these 

 plants, or the sporules producing them, are deposited on the scalp. It will be seen 

 that the appearance of the peculiar porrigo capsule was invariably preceded by a 

 desquamation of the cuticle, that is, a separation or splitting up of the numerous 

 external epidermic scales which constitute its outermost layer. Hence, it is more 

 probable that the sporules or matters from which the vegetations are developed 

 insinuate themselves between the crevices, and under the portion of epidermis 

 thus partially separated, than that they spring up originally below, or in the 

 thickness of the cuticle. 



M. GRUBY accurately describes the mode in which the capsule is formed by 

 the continual growth of the mycodermatous plants, but he says little regarding 

 the manner in which the plants themselves are developed. According to my ob- 

 servations, as soon as the small yellow crust becomes visible, it consists of the 

 outer capsule, formed by epidermic scales, with a layer of amorphous, very finely 

 granulated matter within it, from which spring numerous jointed tubes. Sporules 

 do not appear until later, varying from two to four days ; and their presence in 

 any quantity may be detected by the eye, from their presenting a whitish colour, 

 as M. GRUBY pointed out. In order to examine the development of these vegeta- 

 tions microscopically, it is necessary to make a very thin section of the capsule, 

 completely through, embracing the outer layer of epidermis, amorphous mass, 

 and light friable matter found in the centre. It will then be found, on pressing 

 this slightly between glasses, that the cylindrical tubes spring from the sides of 

 the capsule, proceed inwards, give off branches which in turn terminate in round 



