SqS ANATOMY, 
and feveral other acrid liquors, have a fenfation very like 
to tailing'. Smelling and tailing, every body knows, are 
iubfervient and afliftmg to each other. From fuch exam¬ 
ples. we have further proof of one general caufe of our 
Jenfations, to wit, impulfe from the objects; and of fuch 
a Similarity and relation in the'organs, as might give rea- 
fon for imagining that any one of them would be capable 
of producing the effedt of another, if the impulfesof the 
different cbjedts could be regularly applied to each. 
Hence light and found may a ft e 61 infedts and other ani¬ 
mals that have not eyes or ears. If theimp.ulfe of an ob¬ 
ject is applied with due force, but irregularly, aconfufed 
idea of the objedt is raifed. If the application of theim- 
pulfe is regular, but the force with which it is applied 
too weak, our. perception of the objedt is too faint. One 
may whifper fo low as not to be heard. If the applica¬ 
tion of objects is too violent, and there is any danger of 
the tender organs of our fenles being hurt or deftroyed, 
an uneafy fenfation we call pain is raifed, whatever may 
be the organ thus injured. The object of feeling affedts 
every organ: thus pretfure, ftretching, cutting, pricking, 
acrid (alts, pungent oils, great heat, violent cold, &c. oc- 
calion pain, wherever they are applied. Belides, every 
particular organ can be affedted with pain by the too vio¬ 
lent application of its own proper objedt. Too much 
light pains the eyes; very loud founds (tun the ears; ve¬ 
ry odorous bodies and too fapid objedts hurt the nofe and 
tongue. This is a fure proof that the objedts of ourfen- 
fes all adt, and that the organs are all intpreffed, in near¬ 
ly tire fame way. 
Whenever the uneafy fenfation, pain, is raifed by the 
too ftrong application of cbjedts, a fort of neceflity is as 
it were impofed upon the mind, to endeavour to get free 
of the injuring caufe, by either withdrawing the grieved 
part of the body from it, as one draws back his hand 
when his finger is pricked or burnt; or the injuring caufe 
is endeavoured to be forced from the body, as a tenefmus 
excites the contradiion which putties acrid fteces out of the 
redtum. In both thefe operations, a convulfive contrac¬ 
tion is immediately made in the part hurt, or in the neigh¬ 
bourhood of it; and, if the irritation is very ftrong or 
permanent, the greater part of the nervous fyftem be¬ 
comes affedted in that fpafmodic or convulfive way. Is 
it this neceflity which obliges the mind to exert herfelf in 
refpiration, or in the adtion of the heart, when the lungs 
or heart are gorged with blood ? or the iris to contradl 
the pupil, when the eye is expofed to a ftrong light? or 
fheezing to be performed when the nofe is tickled, &c. 
Will not a ftimulus of any nerve more readily affedl thofe 
with which it is any where connected, than the other 
nerves of the body ? Ma.y not this fympathy ferve as a 
monitor of the mind to employ the organs furniftied with 
nerves thus connedted, to aflift in freeing her of any un¬ 
eafy fenfation, rather than to make ufe of any other or¬ 
gans ? Will not this in fome meafure account for many 
Jalutary operations performed in the body, before expe¬ 
rience has taught us the fundtions of the organs perform¬ 
ing them ? 
This nifus of the mind to free the body from what is in 
danger of being hurtful, may ferve to explain the pheno¬ 
mena of a great many difeafes, after we are acquainted 
with the diftribution of the particular nerves; and from 
this we can underftand the operation of medicines that fti- 
mulate; and may learn how, by exciting a (harp but mo¬ 
mentary pain, we may free the body of another pain, that 
would be more durable ; and that, by having it thus in 
our power to determine a flow of the liquor of the nerves 
to any particular part, for the benefit of that part, or the 
relief of any other difeafed part, we can do confiderable 
fervice by a right .application of the proper medicines. 
OF THE BURSA MUCOSA. 
AS the burfa mucofa are organs which form a very cu¬ 
rious part of our ftrudture, a perfedt knowledge of them 
will frequently be found ufeful in pradtice; yet, notwith- 
(landing the neceflity of being well acquainted with thefe 
material parts of the human frame, anatomifts, even the 
lateft and moil accurate, have not paid that attention to 
the fubjedt which its importance feeirts to require. It is 
well known that the tendons of the mufcles, at the wrifts 
and ankles, and in their courfe aiong the fingers and toes, 
are condudted in (heaths. Window oblerved, that thefe 
(heaths were lined with thin and fmooth membranes; and 
Albinus remarked, that where thefe ligamentary (heaths 
were abfent, facs were frequently interpofed between the 
tendons and the bones over which thefe tendons moved. 
To thefe facs, he gave the name of burfcc mucofa-, and in 
his admirable work, the Hiftory of the Mufcles, he de- 
(cribes feveral of them. Dr. Monro thinks, and not 
without juft grounds, that Window had not lufficiently 
examined the extent and ftrudhire of the membranes li¬ 
ning the ligamentous (heaths of the tendons; and he alfo 
makes it appear, that Albinus did not perceive, as is real¬ 
ly the cafe, any fimilarity between thefe membranes and 
the facs which he defcribed under the name of burfte 
mucofa:. Some of the later anatomifts, profeflor Monro 
thinks, have not lufficiently attended to Albinus’s difco- 
very ; and that others, efpecially the learned Haller, have 
miftaken the nature of the burfa:, fuppofing them to be 
formed of cellular membrane, like that which covers the 
belly of the mufcles; while the greater number of the 
later writers on anatomy have contented themfelves with 
repeating the defcription given by Albinus, and have ne¬ 
ver attempted to throw farther light on the fubjedt. 
The burfte mucofte are only to be found in the extre¬ 
mities of the body ; they are in all 140, thirty-three in each 
fuperior, and thirty -fven in each inferior, extremity. Ma¬ 
ny of them are placed on the inner (ides of the tendons, 
between thefe and the bones. Many others cover not on¬ 
ly the inner but the outer Tides of the tendons, or are in¬ 
terpofed between the tendons and external parts, as well 
as between thofe and the bones. Some are fituated be¬ 
tween the tendons and external parts only or chiefly; fome 
between contiguous tendons, or between the tendons and 
the ligaments of the joints. A few are interpofed where 
the procefles of bones play upon the ligaments, or where 
one bone plays upon another. 
Where two or more tendons are contiguous, and after¬ 
wards feparate from each other, we generally find a com¬ 
mon burfa divided into branches, with which it communi¬ 
cates ; and a few burfte of contiguous tendons communicate 
with each other. Some burfte, even in young and heal¬ 
thy children, communicate with the cavities of the joints; 
and in many old perfons fuch communications are often 
formed by ufe or worn by fridlion, although there had 
been no lamenefs nor complaint of pain made by the per- 
fon on that account during life. There is fome little dif¬ 
ference, in different perfons, as to the manner in which 
contiguous facs communicate with each other, or with the 
cavities of the joints. And, particularly, we have obler¬ 
ved, that a burfa as large as a hen’s egg, which is placed 
behind the tendon of the extenfors of the leg, in fome 
perfons has no communication with the cavity of the joint 
of the knee; but, in the greater number of children, as 
well as adults, we find the opening large enough to allow 
one or two fingers to pafs from the burfa into the joint. 
We are at firft fight (truck with the refemblance which 
the ftrudture of the burfte bears to that of the capfular 
ligaments of the joints; and, the more attentively we pur- 
fue the comparifon, the more juft and perfedt their agree¬ 
ment will be found. 1. The internal membrane of the 
ligaments of the joints, like that of the burfte, is thin and 
denfe. 2. It is connedted to the external ligaments by the 
common cellular fubftance. 3. Between it and the bones, 
layers of cartilage or the articular cartilages are interpofed. 
4. At the lides of the joint, where it is not fubjedted to 
violent preffttre and fridtion, the adipofe fubftance is con¬ 
nedted with the cellular membrane. 5. Within the cavi¬ 
ties of the joints we obferve maffes of fat projedting which 
are covered with fimilar blood-veffels, and with fimilar 
s fimbriae 
