PHYSIOLOGICAL ACTIONS OF DRUGS ON THE SECRETION OF BILE. 259 
reflex expulsion of bile; yet no one has attributed any cholagogue power to 
these. But, without attempting to reason out a question that can only be 
determined by experiment, we would merely add that we leave the investiga- 
tion of the action of drugs on the bz/e-expelling mechanism to those who care to 
enter upon such an inquiry. We are satisfied to have shown that every sub- 
stance supposed to be a cholagogue has, with the exception of calomel (p. 242) 
and magnesium sulphate (p. 164), the power of exciting the bile-secreting 
mechanism; and, as our estimate of their powers, from an observation of the 
bile-secretion only, so closely agrees with observations on the human subject, 
where actions on the bile-secreting and on the bile-expelling mechanisms cannot 
be distinguished from one another, we cannot but infer that surely their actions 
_ on the human subject must be chiefly on the bile-secreting mechanism. 
The term cholagogue is of necessity a vague one, and is applicable to any 
substance that increases the biliary flow, whether by augmenting bile-secretion 
or by exciting contraction in the walls of the bile-passages. We have, there- 
fore, applied the more definite term hepatic stimulant to those substances which 
| we have proved to increase the secretion of bile. 
HEPATIC DEPRESSANTS. 
It cannot fail to strike the reader as a remarkable fact, that while, in the 
| long list of drugs whose hepatic effects we have investigated, we have found so 
| many that stimulate the liver, there is only one—acetate of lead (p. 226)—which 
| appears to have a directly depressant effect. We have, however, found several 
_ drugs that have an indirectly depressant action; thus, when the intestinal glands 
/ are excited to secrete, there is an indirectly depressant effect on the liver, 
| whereby the bile-secretion is lessened. This we have seen to happen when 
magnesium sulphate, castor-oil, gamboge, and calomel are given, and doubtless 
| other purely intestinal irritants have a similar effect. We invariably observed 
| that, while slight purgation—by a purely intestinal irritant—scarcely, if at all, 
| depressed the secretion of bile, powerful purgation produced a very marked 
effect. Why is the action of the liver thus depressed? In our experiments, 
we had to deal with fasting animals, whose intestinal canals contained neither 
bile nor food. Under such conditions, magnesium sulphate could not depress 
the bile-secretion by diminishing the absorption of substances that augment the 
formation of bile. Its depressant effect seems, therefore, attributable either to 
a drain from the portal blood of bile-forming substances, or to an excessive 
lowering of the blood-pressure in the liver, as in the system generally, by a large 
dilatation of intestinal and mesenteric vessels. But when such a purely intes- 
| tinal stimulant as magnesium sulphate is given to an individual under ordinary 
