RECORD OF MEDICAL SCIENCE.
MATERIA MEDICA AND THERAPEUTICS.
Dr. Bernard’s Experiments on the Elective Elimination of certain
Substances by the Secretions.—Dr. Cl. Bernard has written a very
interesting account of certain experiments made by him li on the elective
elimination of certain substances by the secretions, and in particular by
the salivary secretion.” lie remarks in limine that this secretion has
not been examined with the same care as the urine, bile, milk, &c., in
regard of the circumstance alluded to; and that it remains to be
explained how the saliva chooses some, while it rejects other substances
equally soluble in it. lie performed two sets of experiments, which
were ingeniously contrived and carefully repeated.
In the first series of experiments he injected into the right jugular
vein a solution of yellow prussiate of potash, of iodide of potassium,
and of grape sugar, and immediately thereafter he detected the second
substance in the saliva, but neither of the other two; while in the urine,
the prussiate of potash could be detected, but neither the iodide nor the
sugar. Twenty-five minutes after the injection, abundance of the prus-
siate of potash was found in the urine, only a trace of sugar, but still
no iodide. The saliva remained as before. The secretions were tested
every half-hour, but no change occurred till the end of two hours, from
the time after injection, when the iodide of potassium at length appeared
in the urine. Neither the prussiate nor the sugar appeared at any time
in the saliva, which eliminated only the iodide of potassium ; and it is
worthy of remark that this salt appeared immediately in the saliva,
while it was not detected in the urine for two hours. When, however,
the solution of the iodide was stronger, it appeared sooner in the urine,
though never within the hour.
In the second series of experiments, M. Bernard injected these three
substances in solution, severally into the veins of the same animal at
different times, as well as into the veins of different animals, and he
always found that they comported themselves in exactly the same
manner. Such was the case, likewise, when they were introduced into
the stomach. Both grape and cane sugars, like the prussiate of potash,
never appeared in the saliva, while they were eliminated more slowly
by the urine. This observation seemed to contradict the assertions of
some authors, regarding the saliva of diabetic patients, but on actually
testing this secretion in ‘ la Charite,’ M. Bernard found that there was
no trace of sugar in the saliva, while, however, it could be detected in
the expectoration from the bronchi, of such patients as had phthisis
combined w’ith diabetes. Neither sugar nor prussiate of potash would
seem to pass into the bile, or into the pancreatic juice, in ordinary cir-
cumstances, but when sugar was strong in the blood, it was found in
the bile, but never in the pancreatic juice.
In regard to the elimination of sugar from the economy, M. Bernard
has noted a very curious fact, viz., that though the mammary secretion
naturally contains a kind of sugar, it does not allow cither cane or grape
sugar to pass by it. Sugar of milk is much more difficult of fermen-
tation than the other kinds of sugar, and may thus be distinguished
from them.
When the iodide of potassium was injected into the vein of a dog, or
introduced into its stomach, it could always be detected in the saliva
within forty seconds. It also passed with rapidity into the tears, and
into the pancreatic juice, while it passed with much greater slowness
into the bile, in which it was often difficult of detection.
M. Bernard also injected lactate of iron into the veins of dogs, and
never found it eliminated by the saliva; in which respect it agreed with
the sugars and prussiate of potash. When iodide of iron was carefully
injected into the vein of a dog, both iodine and iron were found in the
saliva. In another dog, a solution of the iodide of potash was intro-
duced into the stomach, by a fistulous opening, and afterwards another
solution of lactate of iron ; both substances were thereafter detected in
the saliva, showing that the iodine gave to the iron the capability of
being eliminated by the saliva.
M. Bernard at present merely wishes to call attention to these in-
teresting facts, and does not offer any explanation of them. But the
property which certain substances seem to possess, of being eliminated
by different secretions, is not their only peculiarity. Their period of
sojourn in the economy is also importantly different. Thus, M. Bernard
remarks, that the iodide of potassium and other substances, perfectly
soluble, and really dissolved in the blood, remain for a certain time
within some of the organs of the body; and he finishes his paper with
the following account of the experiments made by him, in order to in-
vestigate this sojourn of the iodide of potassium in the animal economy.
He introduced into the stomachs of several dogs, which had perma-
nent salivary and biliary fistulae, a solution of two grammes of iodide
of potassium. The same day the urine of these dogs exhibited the
reaction of the iodide; next day it could be detected neither in the bile
nor in the urine; and on several days following, no trace of it was found
in these secretions. It seemed to be completely eliminated from the
system ; but examination of the saliva showed its presence still. The
gastric juice also contained the iodide, both because it contained saliva,rand
also because it was furnished directly with it from the mucous membrane
of the stomach. This persistence of the iodide in the saliva and gastric
juice continued for three weeks, and possibly it may have continued
longer. Purgatives have a great effect on the sojourn of the iodide in
the economy; indeed, so much is this the case, that if purgatives were
employed, soon after the introduction of the salt into the stomach, a few
days sufficed for its total disappearance from all the secretions.
In concluding, M. Bernard observes, that these experiments show
that substances which are soluble, and capable of circulating in the
organism without producing mischief, present two sets of phenomena
worthy of remark.
“ 1st. Some substances never pass into certain determinate seeretions,
e. g. the yellow prussiate of potash, cane and grape sugars; others show
themselves in all the seeretions, only with greater or less rapidity, e. g.
the iodide of potassium.
“ 2d. Some of these substances are eliminated completely and rapidly
from the economy, e. g. the yellow prussiate, sugars, &c.; while others
are only partially eliminated by the urine, and may remain in the or-
ganism, showing themselves in other secretions for a longer or shorter
time. The iodide of potassium offers a remarkable example of this pro-
longed sojourn of soluble substances in the organism,—a sojourn which,
in the case of that salt, is prolonged, because the portion not eliminated
and re-appearing in the saliva, instead of being expelled from the system
is constantly thrown, back into the stomach, whence it is taken up by
the circulation, and returned to the saliva, and so on.
“ The chief conclusion,” he continues, “ to be drawn from this work
is, that one cannot refer to any general law, the manner in which these
substances act in the organism. The experiments made on one saline
substance, can teach nothing regarding another : no one could have
foreseen, for example, that the iodide of potassium, and the yellow prus-
siate of potash, salts equally soluble, should offer, in respect of their
passage into the secretions, and of their elimination from the body,
differences very striking. Special researches on each particular sub-
stance are necessary, in order to establish physiological history, which
ought to be intimately connected with its mode of action as a thera-
peutic agent.”—Archives Generates de Medecine, January, 1853.