PATHOLOGY. 
hurried, the colour of the blood will be changed, and 
temperature diminiffed. 
From the circulation of this blood of unnatural qua¬ 
lity, diforder of the .whole of the nervous fyftem, and 
hence of every function in the body, may enfue. If the 
mafs of blood be increafed, and if the aftion of the heart 
be alfo increafed, fo as to propel the greater mafs with 
freedom; in fuch a cafe, the contractility of the fmaller 
arteries being more powerfully oppofed, thefe veflels will 
yield more readily to the current of the blood; they will 
therefore receive a greater quantity of that fluid, and 
confequently an increafed quantity' mull pafs by their 
termination. The quantity of fecreted and of exhaled 
fluids will be increafed ; the blood will flow with greater 
force, and in. greater quantity, throughout the whole 
round of the circulation. As an increafed quantity of 
blood will pafs, in a given time, through the pulmonic 
circuit, refpiration mu ft be more quickly performed, 
otherwife’that fluid will not duly undergo the pulmonic 
procefs. The fenfibiiity of the nervous fyftem may be in¬ 
creafed, and the functions of that fyftem may be more 
freely performed. Hence all the functions dependent on 
nervous influence will be exalted. 
The diminution of quantity in the blood generally 
manifefts itfelf by the want of aftion in the nervous fyf¬ 
tem, and hence of ail the Accretions. But this ftate is 
not likely to laft long; and indeed generally remedies it¬ 
felf, except when the affimilating organs of the body are 
difeafed. 
Faffing over thefe plethoric ftates, we come to the con- 
fideration of an alteration in the contraftility of the 
blood-veffels, or of the common malady called inflam¬ 
mation. 
When a violent blow is given to an external part of the 
body, the four following circumftances are after a time 
obfervable; viz. rednefs, tumefaftion, pain, and heat. 
Prefently a- throbbing is felt in the arteries going to 
the part, and a difturbance takes place in the vafcular and 
nervous fyftem, concifely called fever, and a change in 
the quality of the blood. To account for thefe fimple 
appearances has puzzled the medical philofophers of 
every age, and it puzzles them fill!. In our Introduction 
we have noticed the wild fpeculations of the earlier phy- 
flcians. Faffing over Boerhaave’s notion, that vifcidity 
of blood was the caufe of inflammation, and that of Cullen, 
which, like this theory of fever, refts on the affumption 
of a fpafm of the extreme arteries, we proceed to notice 
the celebrated opinions of Mr. John Hunter. According 
to him, inflammation is to be conlidered only as a difturbed 
ftate of parts, which requires a new but falutary mode 
of aftion to reftore them to that ftate wherein a natural 
mode of aftion alone is neceflary. From fuch a view of 
the fubjeft, therefore, inflammation in itfelf is not to 
be conlidered as a difeafe, but as a falutary operation, 
confequent either to fome violence or to fome difeafe- 
Effewhere the author remarks, the aft of inflammation is 
to be conlidered as an increafed aftion of the veflels, 
which, at fir ft, confifts limply in an increafe or diftention 
beyond their natural lize. This increafe feems to depend 
upon a diminution of the mufcular power of the velfels, 
at the fame time that the elaftic power of the artery mult 
be dilated in the fame proportion. Owing to this dilata¬ 
tion, there is a greater quantity of blood circulating in 
the part, which is according to the common rules of the 
animal economy: for, whenever a part has more to do 
than Amply to lupport itfelf, the blood is there collected 
in larger quantity. The /welling is produced by an ex- 
travafation of coagulable lymph, with fome ferum ; but 
this lymph differs from the common lymph, in confe- 
quence of palling through inflamed veflels; it is this 
lymph which becomes the uniting medium of inflamed 
parts; veflels Iboot into it, and it has even the power of 
becoming vafcular itfelf. The pain proceeds from fpafm. 
The rednefs is produced either by the arteries being more 
dilated than the veins, or becaufe the blood is not 
193 
changed in the veins. When, after an ibjury, a part 
cannot be reftored to health by inflammation alone, or by 
adhefion, then fuppuration, as a preparatory ftep to the 
formation of granulations, and the confequent reftora- 
tion of the part, takes place. The veflels are nearly in 
the fame ftate as in inflammation ; but they are more 
quiefcent, and have acquired a new mode of aftion. See 
Hunter on the Blood, Inflammation, &c. 
That the capillaries are diftended in inflammation is 
pretty generally agreed ; and, this allowed, we clearly ex¬ 
plain the increafed fize of the part, without admitting 
that lymph is extravafated, a faft of which we have no 
proof. 
We have not fpace to enter at full into the proofs of 
the diftended ftate of the capillaries. There is lefs dif- 
cuffion required about this diftention, however, than it 
has been the falhion to enter into ; for it is vifible to the 
naked eye, and is (till more clearly ihown by the micro- 
fcope. The independence of this diftention on the 
heart is alfo pretty clearly eftabliffied; for we obferve 
bluffing from fliame or ire, and a rednefs in various 
parts of the body, without general accelerated pulfe. 
But, though the diftention of the capillaries in inflam¬ 
mation is pretty generally allowed, pathologifts are by 
no means agreed as to the rate of motion which the 
blood undergoes in them; fome, as Wilfon, aflerting 
that the velocity of the blood through an inflamed part 
is diminiffed; others ftating that it is increafed. Dr. 
Parry fliows very clearly, that this is of little confequence 
to our fpeculations on this fubjeft; but properly remarks, 
that, if the velocity be diminiffed, yet, the quantity be¬ 
ing increafed, the momentum mult ftiii be greater than 
ordinary. Again ; a queftion arifes, whether the arte¬ 
ries retain during inflammation the alternately-contrail¬ 
ing force which we have affigned to them in health, or 
whether this power is loft. The proofs of the firft alter¬ 
native reft on what is obferved by means of the micro- 
fcope on the tranfparent parts of cold-blooded animals; 
as, for inftance, on the web of a frog’s foot. It is- there 
feen, that, on the application of ftimuli to a certain de¬ 
gree of force and for a certain time, a permanent or un¬ 
varying dilatation of the capillaries fupervenes, and the 
blood feems to move (lowly. This obfervation is not 
worth much, however, becaufe even the alternate con¬ 
tractions of the capillaries are not vifible in the fituation 
above mentioned, on account of the fmall fize of the 
veffel. We may adduce a pathological obfervation more 
ftrongly corroborative of the inert dilatation of the capil¬ 
laries in inflammation ; which is, that, whereas the ex- 
hauftion of the contents of arteries (not having been 
thus aft'efted) is met with almoft invariably, inflamed ar¬ 
teries are not exhaufted of their blood. 
The pain in inflammation is not eafily accounted for. 
That the fenfibiiity of the nerves is much increafed is 
evident from the extreme uneafinefs which ordinary im- 
preffions produce on them when in a ftate of inflamma¬ 
tion ; but we are ignorant by what means this pain is 
produced-; It has been attributed to the preffure of the 
diftended capillaries ; and this appears plaufible at firft 
view ; Lut the idea is oppofed by the fails, that many 
parts fuffer diftention of their capillary veflels without 
pain occurring; and that the-pain is often mod fevere 
before this diftention begins ; as for inftance, after a blow, 
or in the cafe of gout, in which difeafe, as is well known, 
the coming-on of rednefs and fwelling often relieves the 
excruciating pain of the firft attack; fo that we are com¬ 
pelled to ftate increafed fenfibiiity as one of the eflential 
circumftances of inflammation, but we cannot trace the 
caufe of its produftion. The increafed warmth of the 
part has been fuppofed to depend upon the prefence of 
an increafed quantity of blood. But, as the extrication 
of heat is a procefs which is dependent upon the ner¬ 
vous fyftem,and confequently influenced by altered con¬ 
ditions of that fyftem, the increafed warmth, and the in¬ 
creafed evolution of heat, which accompany inflamma¬ 
tion, 
