On Plica Potonica, 329 
have been preferved, and even nitrous acid diluted 
with water. 
Since no other caufe can be affigned for this difeafe, 
it is probable, that it arifes, according to the general 
Opinion, from contagion; a contagion which, like 
that of Pfora, can be communicated by contact only: 
but this I have not been able to afcertain by any 
obfervations of myown, __ 
It is faid, however, by authors of reputation, that 
Plica is frequent in Tartary ; and that it was brought 
into Poland in the thirteenth century by the Tar- 
tars, who at that period made frequent irruptions 
into the eaftern parts of Europe. 
A perfec confidence in the liberality and candour — 
of a Society, the exertions of which have added 
confiderably to the treafures of fcience, encourages 
me to fubmit to it thefe few crude and curfory re- 
marks ; trufting that the moft trivial contribution to 
the general ftock, will not be deemed unworthy its 
attention. At fome future period I hope to have 
opportunity and leifure to renew my obfervations 
upon the fubject; and I fhall endeavour to fupply ' 
the deficiences of the prefent Sketch, by tranfmitting 
to. the Society the refult of my future remarks. 
