(seq. 61)

52

Materia Medica

Astringents

colour of the skin which it acquires and the thickening and
condensation of what is called sole leather. On the living
animal skin it cannot penetrate farther than the epidermis
and acts only by its impression on the surface. Dr More of
London says they have not the power of causing contraction
of the living fibres and from one of his experiments it
appears that the quantity of perspirable matter was
increased by application of astringent matter, into a strong
Decoction of oak bark he immersed one hand and the
other in water of the same temperature and then covered
both with a glass vessel, upon examination he found the
quantity of perspirable matter discharged and contained in
the vessel greater from the hand emersed in the
astringent decoction, but it is evident they do not produce a
contraction and condensation of muscular fibers when
applied externally thus when a piece of allum is applied
to the tip of the tongue this effect is very obvious. Dr
Darwin supposes the allum stimulates the absorbents
of the tongue by which the more fluid parts are taken up
some authors suppose astringent to act beyond the