734 TINEA TONSURANS. 



PatJiology. — " The nature of this disease Is to he studied in the 

 Lotany of the cryptoganiic parasite called the ' Ti'icophytan, dis- 

 covered by Malmsten in 1845. It consists of oval transparent 

 Bjiores or globules, about t-dVit V^^^ °^ ^°- i^ch in diameter, 

 ^lany of these are isolated, others constitute by their juxtrjpositioix 

 articulated filaments. Its anatomical seat is the interior of the 

 roots of the hair. The hairs and fungi simultaneously inoreaac ; 

 the former seem larger than usual, are paler in colour, loaa 

 their elasticity, soften, and break off when they have risen somsi 

 one or two lines above tlie svirface." — (Aitkex.) 



Iiing-Avorm may affect any part of the animal body, but it^^ 

 fnvovirite seats appear to be the hind cj^uartors, back, neck, and 

 face. It is a contagious disease, and depends upon tlie presence 

 of the vefjetable parasite already described. It differs fi-om favu3 

 in the colotir of the scabs, which are greyish-wliite instead oft 

 yellow. The microscopic appearance of the plant, its structure, 

 and its powers of propagation are identical with the Acho»ioa 

 Schonleinii. " There are numerous facts which justify the beUcfj 

 that there exists but one essential fungus, whose sporulcs find a 

 Bpil for development and grQ\\'ih -upon the surface, or even within 

 more secluded portions of the body ; and that varieties in tha 

 f^rowth of that fvmgus are due to differences in the constitution: 

 of the individual, to t]ie moisture, exudation, soil, or tcmpcrahxiu 

 under which the development of the fungus takes place. The 

 exart nature of these differences is not yet understood ; but tlie 

 production of irritant acids and gases are constant accompani- 

 ments of the growth of such parasites, by the chemical action of 

 the vegetable cell : for it does not undergo development without 

 oxcitiug a chemical decomposition in the pabulum on which it 

 feeds, and the different stages in iU growth give rise to alcoholic 

 acid and putrefactive fermentations. Thus tlieir irritant action 

 very soon may establish an eruption. But the ratio of eruption 

 to parasite is not constant ; for an amount of fungus which will 

 simply prodxice the death of hair in one person or part of the 

 body, mny in another produce irritation, eruption, or violent 

 inflammation. These different results may be due to two causes 

 — (11 constitutional peculiarity in different indiA^duals ; (2), 

 peculiarity of structure of a part as regards density, heat, mois- 

 ture, and chemical and anatomical composition of the part." — 



(AlTKEN, IvOWE.) 



E.xperiments are wanting to prove the possibility of the ring- 



