164 
REVIEW OF MOIROUD’s 
however, are imperfections from which the most methodical 
classifications are not always exempt. 
First Class of Special Excitants. 
Purgatives and Laxatives. 
This title, which sufficiently expresses the primitive and most 
constant and marked effects of these agents, does not prejudge 
the intimate action which they exercise on the living surface 
with which they come in contact. Each of the substances which 
will pass in review seems to have an action peculiar to itself, 
and different more or less from that, of all others. We must, 
however, unite under some common designating terms those 
whose effects are most analogous: thus we divide them into lax¬ 
atives and cathartics , and the latter into mild (minoratifsj , and 
drastic or strong. 
The difference of action between the mildest laxatives and the 
most drastic medicines is sufficiently marked, but the line of demar¬ 
cation between many of the intermediate substances can be with 
difficulty drawn. We can also produce with the same substance 
effects exceedingly different, according to the dose and the cir¬ 
cumstances under which it is administered, yet still the peculiar 
character of each drug being retained ; for the drastic will irritate, 
even in small doses, and the laxatives, in a large dose, will pro¬ 
duce abundant evacuations without irritation. 
The purgatives rouse the sensibility of the mucous membrane 
with which they come in contact: they produce redness and 
turgescence of the membrane, development of the capillary ves¬ 
sels, and increased exhalation and secretion. The irritation is 
soon propagated to the muscular tunic, which accelerates the 
peristaltic motion, and causes a speedier and fuller evacuation of 
the contents of the intestinal tube. This influence extends to 
the liver and the pancreas, which pour out more abundantly 
their peculiar secretions. 
These phenomena, however, although connected with the ac¬ 
tion of almost every purgative, vary in each. In some the in¬ 
testinal and hepatic secretions are abundant, but there is not 
much increased peristaltic motion, nor any copious evacuation 
of solid matter ; in others there is little discharge of bile or 
fluid, yet the dejections are frequent and abundant. Some pur¬ 
gatives act on the whole extent of the intestinal canal; others 
confine their principal influence to one portion or part. Some 
affect the small intestines chiefly; others almost exclusively the 
colon and rectum. Some drugs, exceedingly irritating and dan¬ 
gerous, and that frequently produce intense inflammation of the 
