00 P A T H O 
half of laudanum taken into the ftomach will commonly, 
but not always, produce death ; we have no hefitation 
in afiigning the laudanum as the caufe of death, in thofe 
inftances in which death takes place, notwithftanding 
there are other inftances where the obvious circumftances 
are alike, in which it is not followed by death. Inva¬ 
riable fuccejfion bears fo ftrong an analogy to caufation, 
that we fcarcely fufpedt the pofiibility of our being de¬ 
ceived in an inference grounded upon it; and yet we do 
fometimes make a falfe inference founded upon paft inva¬ 
riable fucceftlon, as is proved by additional, or fubfe- 
quent, experience. Frequent fucceftlon of like to like, 
bears an analogy to the invariable, and upon this analogy 
we found an inference of caufation : the point of ana¬ 
logy is between the frequent and the invariable , confe- 
quently the analogy mult be eftabliftied or prefumed upon, 
in proportion to our experience of the frequency of the 
fucceftlon of like confequences to like antecedents. 
Thefe grounds of the inference of a caufe, as is juft 
ftated, are imperfedt, and rnuft admit frequent error; 
for we cannot define what number of fuccelftons of like 
confequences to like antecedents, are an adequate num¬ 
ber to prove caufation. Hence then, although we in¬ 
fer caufation from fucceftlon, we are obliged to confefs 
that we can do this only in certain cafes; before we can 
admit the truth of an inference of caufation, we muft 
have iiad an experience of a fufficient frequency of a 
like fucceftlon. Different men will hold different opi¬ 
nions with regard to what conftitutes a fufficient fre¬ 
quency, and the want of a poftible definition in this 
matter admits a great diverfity of opinion upon impor¬ 
tant points, and gives room for the diftindtion of clofe 
and loofe reafoners. But, when once we have had expe¬ 
rience of what is confidered a fufficient frequency of like 
fucceftlon, wejhen infer fome difference (where it is not 
perceptible) in cafes in which the fame confequences do 
not fucceed the fame antecedents. In fuch inftances, 
we balance an account between like and diflimilar fuc- 
cefilon ; and we affign a caufe only where the frequency 
of the fame fucceftlon (approaching to the invariable ) 
exceeds that of the exceptions. Thus, (not to quit our 
fubjedt,) if the exhibition of a particular medicine 
fliould be followed by recovery from phthifis pulmonalis 
in one inftance, this fucceftlon would, where men are 
difpofed to catch at ftraws, indicate a poftible caufation ; 
if the fame event fucceeded to its exhibition in ten in¬ 
ftances, its credit would be better fupported; if in a 
hundred, better Hill. If it fliould fucceed in five and 
fail in five, we fliould hefitate perhaps tc aftign it as the 
caufe of recovery in the firft five; if afterwards it fliould 
fail in fifty cafes, we fliould fay that in the five in which 
it W’as followed by recovery the cure was owing to oilier 
caufes. If it fliould fucceed in a hundred and fail in fifty, 
we fliould then perhaps judge the hundred to amount to 
an adequate number to eftablifli the relation of the medi¬ 
cine, as a caufe of recovery ; while we fliould explain its 
failure in the other fifty, by fuppofing fome diverfity of 
circumftances, by which its relation as a caufe was modi¬ 
fied, to have prevailed. The conclufion amounts to this : 
We infer that a fecondary is produced by a primary dif- 
eafe, upon an experience of a frequent fucceftlon of the 
one to the other, provided at the fame time that our ex¬ 
perience furnifhes us with no ftronger analogies to fenfi- 
ble caufation, by which we are rather juftified in confi- 
dering them diftinft.” Pring, ch. iv. 
This fucceflion of difeafed actions in many difeafes pro¬ 
duces acurative effedl; and the contemplation of this fadtis 
what has caufed fo many errors to be committed in practice 
in regard to the operation of nature. Seeing that thecon- 
ftitutional difturbance produced a reftoration of health in 
local difeafes, Hippocrates, and thoufands fince his time, 
liftve been led to the adoption of that inert practice em¬ 
phatically termed the “ Medicine expcdlante." It has 
always been a popular dodtrine, and it is one that carries 
a great deal of plauflbility in the face of it, that the 
LOGY. 
main objedt and the fum total of the powers of medi¬ 
cine, confift in aiding the natural efforts of the conftitu- 
tion for the removal of difeafes. But this propofltion 
requires confiderable qualification. If it be merely meant, 
that medicine can only operate through the medium of 
the powers or energies of the living body, and that, in¬ 
dependently of thefe vital energies, medicine has no 
operation, the pofition is a truifrn which cannot be quef- 
tioned. But, if it be meant that the foie power and ob¬ 
ject of the medical art are limited to the furthering of 
all morbid excitement, and to the removal of obftacles 
to the completion of the purpofes of that excitement; 
i. e. to aflifting the efforts of nature, or guarding them 
from interruptions ; the affertion appears to be altoge¬ 
ther gratuitous, and nothing lefs than an abufe of lan¬ 
guage. In the firft place, it is founded on the affumption, 
that all difeafed adtion is falutary; which the effedts of 
numerous difeafes diredtly contradidt, and which has no 
better foundation than two other gratuitous affumptions, 
namely, the exiftence of a morbid ferment in the blood, 
and of an archeus, or rational foul, governing all the 
operations of the animal economy. But, fecondly, ad¬ 
mitting the falutary tendency of difeafed adtions, confi¬ 
dered as the efforts of nature, by what figns are we to 
interpret her intentions, or to difcover when (lie requires 
affiftance, and when reftraint ? On this point the greateft 
practical errors are likely to be committed, and have, in 
fart, been conftantly and extenfively committed, by thofe 
humoral pathologifts, who have prefumed upon their 
knowledge of the intentions of Nature. 
Another popular and general opinion arifing from the 
obfervance of this fucceftlon of difeafed adtions, and 
connedted likewife with the humoral pathology, is the 
dodtrine of metaftafis, or tranfpofition. It is found, that, 
on the difappearance of an eruption of the fkin, inflam¬ 
mation of fome of the vifcera often takes place; and 
again, that the cure of gout in the extremities fometimes 
produces very formidable eft'edts on the brain. Hence it 
was fuppofed, that there was an abfolute tranflation of 
fluid to the part fecondarily affedted. On this fubjedt, 
however, as we again find fome matter of an important 
nature in Mr. Pring, wefliall make another extradt. 
“ That certain difeafes are related with'each other in 
the way of caufe and effedt, is a remark which is contem¬ 
porary with the earlieft records of medical obfervation. 
It is alfo a piece of information popular with all claffes, 
that the cure of one difeafe, whether fpontaneous or by 
art, is fometimes followed by the occurrence of another. 
Thus, it is common to expedl a favourable change of 
fome internal difeafe upon the occurrence of a cuta¬ 
neous eruption; thus, alfo, it has fallen under the ob¬ 
fervation of the ignorant and unprofeflional, that a cuta¬ 
neous difeafe, cured by external applications, often pro¬ 
duces vifceral difeafe. The language of the vulgar in 
the firft of thefe cafes is, that the internal difeafe is 
coming out ; in the fecond, that the difeafe of the fkin is 
thrown in, or fettled upon the lungs for inftance. To 
all phyflcians the clafs of fadts here adverted to is well 
known ; they have been made the fubjedt of exprefs 
treatifes, and have been remarked upon in every age, and 
explained according to the prevailing pathology of the 
times. But the profeffors of medicine have of late been 
rather fceptical with refpedt to the affigned agency of the 
phenomena in queftion, though it is not improbable that 
their exception was taken rather againft the dodirine of 
humours, See. by which the phenomena were,explained, 
than againft the more modeft inferences which they 
might be allowed to furnifli. To all phyficians of the 
prefent day the clafs of fadts, defignated as thofe of re¬ 
lated difeafe, is well known : by fome, thefe facts are not 
fuffered to furnifli an inference of a relation, that is, they 
are confidered independent of each other; others admit 
the relation, and explain it in the language of the vul¬ 
gar ; others fay that one difeafe, inftead of falling or be¬ 
ing thrown upon another part, is converted into a difeafe 
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