21G 
PATHOLOGY. 
violent inflammations contagious effluvia may be fecreted. 
In common ftates of the atmofphere, this is probably 
mixed, diffufed, and decompofed ; but in peculiar con¬ 
ditions of the air a fufpenfion may take place, and thus 
contagious fever may be rendered general. Now that 
the morbid fecretions of the mucous membrane are con¬ 
tagious effluvia, and that thef'e are modified by nervous 
impreflions in the fame way as all fecretions are, feems 
rendered (till more probable by the circumftances, that in 
thofe fevers which are molt contagious, viz. the exanthe¬ 
mata, a phlogofed ftate of the mucous membrane is uni¬ 
formly prefent, and that an emetic exhibited early in 
thofe maladies often prevents the attack; a faft which 
we can only explain on the fuppofition that this remedy 
actually removes a depofited fecretion, or, in other words, 
contagious effluvia from the furface of the ftomach. In 
faff, there feems good evidence in fupport of the opinion, 
that all inflammation of, or difordered fecretion in, the 
mucous membrane may elicit contagious effluvium. 
Thus dyfentery, cholera, eryfipelas, the influenza, (a 
fpecies of catarrh,) have all been fometimes contagious, 
though it is well known that all thefe difeafes occur 
without fucli an effect being produced. Nor, can we, 
on the fame account, difmifs with the abfoiute denial 
which molt authors have thought proper to do, the well- 
fupported aflertion, that croup and phthifis are occafion- 
ally catching. 
To return to the yellow fever; it is to be remarked, 
that a confideration of the medical topography of the 
countries where this fever has appeared mult difclofe 
grand and important circumftances relative to the ma¬ 
nagement of our fleets and armies. As this fubjeft, 
however, embraces a wide field in a branch of medical 
fcience hitherto not cultivated fyftematicaliy, we regret 
that our limits will not permit us to difcufs it fully ; 
but we can, with the utmoft confidence, refer our read¬ 
ers to a work by Dr. James Johnfon on Tropical Cli¬ 
mates; which contains all that is at prefent known on 
the fubjeft. 
As to the nature of yellow fever, its immediate 
caufes operate of courfe, as in other fevers, through the 
medium of the mucous membranes; and the irritation 
which is communicated to the brain and fpinal marrow 
forms the grand connefting and eflential link to the de¬ 
velopment of the general febrile phenomena. The ac¬ 
tion of the predifpoling caufes, as climate, fatigue, &c. 
is however to render the mucous membranes particularly 
liable to inflammation ; while the fame influence, by af- 
fefting the circulation of the furface, as was (liown when 
treating of Cholera, throws unnatural quantities of blood 
into the portal fyftem, and produces congejlion there, 
this being the only part of the venous fyftem where 
fucli a ftagnation can take place. The eft’eft of this is 
particularly felt in the liver, the ftoinach, and indeed 
the whole abdominal vifcera. 
The charafteriftic fymptom of this fever, viz. the yel¬ 
low colour of the fkin, is varioufly accounted for by dif¬ 
ferent authors. Dr. Bancroft fuppofes it is induced by 
the preflure to which the aft of vomiting fubjefts the li¬ 
ver and gall-bladder. But to this it is replied, that 
there is no proportion between the intenfity of colour 
and the feverity of the vomiting; and moreover, that 
it often occurs before the vomiting takes place. Brouf- 
fais is of opinion, that the yellow colour depends on 
violent irritation of the duodenum propagated to the fe- 
cretory organ of the bile. The moft plaufible opinion, 
however, though it has been much ridiculed, feems to be, 
that the fufpenfion of the aftion of the liver prevents the 
elimination from the blood of the bilious elements, and 
that thefe, exifting in the blood from the want of fecre¬ 
tion, and not from abforption, produce the phenomena 
in queftion. We have fome reafon to believe, that a 
morbid ftate of blood might caufe the fame appearance 
without the liver being materially implicated. This 
indeed, as far as regards certain yellow dingy patches 
which occafionally appear on the (kin in this fever, is al¬ 
lowed by Dr. Bancroft. 
The black vomit, a moft formidable fymptom in yellow 
fever, was for a long time attributed to a fuperabundant 
and altered fecretion of bile; but certainly without foun¬ 
dation, as is evident from the faft, that in a great number 
of difleftions the liver has been found in a healthy ftate; 
and, where it has differed from its natural appearance, it 
has frequently been of a paler colour; the gall-bladder 
has alfo at the fame time been found in a healthy ftate, 
containing its ufual quantity of bile, not at all altered in 
its appearance or properties. Moreover, at a time when 
the ftomach has been diftended with black vomit, the paf- 
fage from the duodenum into the ftomach has been com¬ 
pletely obftrufted by the pylorus valve, fo that no portion 
of the matter could have been derived from the hepatic fyf¬ 
tem, in every part of which fyftem the bile was quite natu¬ 
ral in colour, tafte, and confiftence. The matter of black 
vomit, compared with bile, differs materially from it in 
all its phyfical qualities. It differs from it in colour; for, 
however dark the bile may appear in its moft concen¬ 
trated ftate, it always difplays a yellowifh or greenifh- 
yellow tinge, when fpread on a white furface, or when 
diluted ; and this is never obferved with the matter of 
black vomit. Indeed Dr. Bancroft has found that an 
addition of bile to the latter, altered its nature fo much 
as to give it an appearance different from what it had be¬ 
fore ; nor could the black vomit be imitated by any mix¬ 
ture of various proportions of dark-coloured bile with 
the fluids found in the ftomach. It differs moft deci¬ 
dedly in tafte; the black vomit being always infipid, 
when freed from other foreign matters; whereas the bile 
can never, by any means, be deprived of intenfe bitter- 
nefs. 
A natural conclufion therefore is, that the black vo¬ 
mit proceeds from the ftomach itfelf, and is a confequence 
of inflammation of that vifcus; whether this be a par¬ 
ticular morbid fecretion by the inflamed veffels or glands 
of the ftomach ; or, as Dr. Bancroft thinks, “ merely 
blood which has been effufed from fome of the fmall ar¬ 
teries, ruptured in confequence of the feparation of cer¬ 
tain portions of the villous coat-, and which has coagu¬ 
lated within the general cavity of the ftomach, or on the 
furface over which it was effufed ; and, having been af¬ 
terwards detached and triturated by the violent and fre¬ 
quent contraftions of that organ in the efforts to vomit, 
has had its appearance as a coagulum of blood altered, 
and its colour darkened by the gaftric juice, or by fome 
chemical decompofition, either fpontaneous, or produced 
by the aftion of the air, or other matters contained in 
the ftomach.” 
It remains to give a defcription of the fymptoms of 
this fever, which we believe will be found to agree accu¬ 
rately with the above fhort pathological lketch. The 
defcriptions, not being drawn from our own obfervation, 
are felefted from the moft accredited authors, whofe 
names we fhall fubjoin. The chief diftinftions between 
the different forms this fever exhibits are drawn from its 
violence, or, what amounts to nearly the fame, its con¬ 
tinued, its remittent, or its intermittent, form. 
The firft defcription is that of Dr. Bancroft, derived 
from the contemplation of this fever in the weftern he- 
mifphere. “ The progrefs and violence of the yellow 
fever differ greatly, according to the force of its caufe, 
the vigour and excitability of the patient, and the feafon 
of the year. When it prevails epidemically in hot cli¬ 
mates, and attacks young and robuft men, lately arrived 
from temperate regions, the diforder commonly appears 
in its moft aggravated form. In this, the patient firft 
complains of laflitude, reftleffnefs, flight fenfations of 
cold and naufea, which fymptoms are foon fucceeded by 
ftrong arterial aftion, intenfe heat, flufhing of the face, 
rednefs of the eyes, great pain and throbbing in the head 
and in the eye-balls, uneafinefs and pain in the ftomach, 
opprefflon of the praecordia, a white fur on the tongue. 
