Mettauer on the Crusta Genu Equina in Epilepsy. 195 
a little sooner by gentle solicitation, and occasionally by firm 
compression with a bandage. This should be suffered to re- 
main on after the period of disquamation is near at hand, to 
prevent the accidental loss of the crust. After it is obtained, 
it should always be dried a short time in the shade, and then 
it may be kept for use in a close jar, to prevent, so far as pos- 
sible, the escape of its volatile properties. 
We have to regret our inability to furnish a correct, or even 
a tolerably satisfactory chemical analysis of the crust ; from 
what has been ascertained, the urate of soda seems to be one 
of its principal constituents ; we are inclined to believe that 
ammonia, in combination with perhaps the lithic acid, may 
also enter into its composition : from the peculiar compound 
odour which it often inhales, much resembles that emitted by 
common urine after standing some time. 
Two forms for administration are only used — the powder 
and tincture. When the powder is to be used, it should al- 
ways be freshly prepared, either by pounding and rubbing the 
dry crust in a mortar, or by grating it with a common nut- 
meg grater : this last process will be found, (generally,) most 
convenient, as it enables the practitioner to reduce it, at once, 
to a very fine and equable powder, even if the crust is im- 
perfectly dried. 
The tincture is prepared by simply digesting the broken or 
powdered crust in diluted alcohol, or common brandy, exposed 
to a gentle heat for eight or ten days in the proportion of one 
part of the former to four of the latter. 
The doses of the powder vary from two to twenty grains ; 
it may be given diffused in any liquid which the patient fan- 
cies. With young patients it is safest to begin with the mini- 
mum, and increase very gradually to the maximum doses. 
Should the disease yield before the largest doses are reached, 
no further augmentation need be made. When the tincture 
is employed, from 3ss. to ^iss. are its extreme doses. Diluted 
with water and sugar, it may be given with very little diffi- 
culty to the youngest subjects, as it is tasteless, and in a great 
measure inodorous. In this form also, the doses should be 
very gradually increased, to prevent, as far as possible, the 
