38 
REVIEW OF MOIROUD's 
tlie blood, and render it less stimulating. Sedative medicines 
act principally on the fluids ; tonics on the solids. 
The immediate action of medicines on the tissues with which 
they come in contact is the most simple, and generally the most 
advantageous; their effects, however, are not confined to this place, 
but, by contiguity of tissue, or by absorption or sympathy, exert 
a more extensive influence. Of the influence communicated by 
contiguity of tissue, we have frequent proof, as when we calm the 
inflammation of the mucous membrane of the respiratory pas¬ 
sages by emollient drinks, whose sedative effects are transmitted 
to these passages through the medium of the pharynx, with 
w hich the drink comes into contact; and as emollient cataplasms 
applied to the loins in inflammation of the kidneys extend their 
soothing influence through the medium of the intervening tissues. 
Of all the means by w hich medicines extend their action, there 
is no one so general or so complete as absorption: they are 
carried into the circulatory current, and conveyed with it to every 
part of the frame, and thus exert a direct influence on the 
whole organization. Salts of iron and .copper, and resinous 
substances, administered by the mouth, have been speedily 
detected in the blood by chemical analysis. Their stay in the 
circulatory vessels is ordinarily of short duration; for if they 
cannot assimilate themselves with some organ or tissue, they 
are discarded by the natural emunctories: thus the cutaneous 
perspiration, and pulmonary exhalation betray the odour of 
ether; the milk obtains the bitterness of w ormw ood, and the 
urine is charged with certain metallic oxides. 
The rapidity of the circulation explains the promptitude of 
effect often produced. M. Hering proved that it occupied but 
thirty seconds to carry prussiate of potash from one jugular to 
the other; and in a few minutes the serous and mucous exhala¬ 
tions were impregnated with this salt. 
Many drugs are, however, easily assimilated, of which the 
combination of the colouring matter of madder with the earthy 
portion of the bone, the bitter taste contracted by the flesh of 
animals fed on bitter herbs, and the intimate union of the 
prussiate of potash with the 
are sufficient proofs. 
Many circumstances influence the rapidity of absorption. To 
produce ready absorption the medicines should be soluble in 
water and miscible with the blood. Insoluble matters penetrate 
with difficulty into the absorbents, and often do not penetrate 
at all. Absorption is slow when the mass of fluid actually in 
circulation is considerable, and is often rapidly promoted by the 
parenchyma of almost every organ 
