HoGG_, on Parasitic Fungi. 
41 
form and size of the spores and mycelium. The spores of the 
Achorion Schoenleinii are oval and comparatively large, 
whilst those of Trichophyton tonsurans are spherical and 
small. M. Gruby gives the following directions for making 
examinations of the products of Favus^, and which answers for 
the examination of other skin diseases. He says, in order to 
examine the natural position of these fungi microscopically 
in the animal cutaneous structures, it is necessary to make a 
thin section of the capsule completely through, embracing 
the outward layer of epidermis, amorphous mass, and light 
friable matter found in the centre. It will then be found, 
on pressing this slightly between glasses, and examining it 
with a magnifying power of 300 diameters, that the cylin- 
drical tubes [thalli) spring from the sides of the capsule, 
proceed inwards, give off branches dichotomously, which, when 
fully developed, contain at their terminations [mycelia) a 
greater or less number of round or oval globules (sporidia) . 
These tubes are from the -^-J oth to ^ J^th of a millimetre in 
thickness, jointed at irregular intervals, and often contain 
molecules, varying from ^oo^o?)^^ to yo^^ ^th of a miilimetre in 
diameter. The longitudinal diameter of the sporules is 
generally from -3-o oth to yjo^h, and the transverse about the 
same (Gruby) . The mycelia and sporules agglomerated in 
masses are always more abundant and highly developed in the 
centre of the crust. The thalli on the other hand are more 
numerous near the external layer. 
There may frequently be seen swellings on the sides of the 
jointed tubes, which are apparently commencing ramifica- 
tions. On examining the hairs which pass through the favus 
crusts, it will often be found that they present their healthy 
structure ; at other times, however, they evidently contain 
long, jointed branches, similar to those in the crust, running 
in the long axis of the hair, which is exceedingly brittle. I 
have generally found these abundant in chronic cases ; and 
on adding water, the fluid may be seen running into these 
tubes by imbibition. There can be very little doubt that the 
tubes and sporules, after a time, completely fill up the hair- 
follicle, and from thence enter the hair, causing atrophy of 
the bulb and the baldness which follows the disease.^ 
PoRRiGO DECALVANs. Syu. Tinea decalvans, Alopecia 
circumscripta. 
The fungus known by the name of Microsporon Audouini, 
is said to cause this disease, and the light-gray crusts which 
* Dr. Bennett's 'Principles and Practice of Medicine/ p. 801, 2d edition. 
