SS8 ANATOM Y, 
wards, the fubtle particles or imprefllons of fome things mere decreafe of cutaneous tranfpiration, occafioned by 
applied to the (kin. The (in'! of thefe three ufes depends the continual reft and inaction of thefe animals, has a great 
on the extremities of the nerves ; the fecond, on the arte- (hare in this effect. 
rial productions; and the third, on the origin of the ab- 
forbent fyftem. The cutaneous glands fecrete an oily hu¬ 
mour of different confidences. But, without the epidermis, 
both papillae and glands would be difturbed in their func¬ 
tions ; on which great di(orders niuft enfue. The epi¬ 
dermis ferves to jceep the pencils or nervous filaments of 
the papillae in an even fituation, and without confufion; 
and it likewife moderates the impreftions of external ob¬ 
jects. Particular as well as general feeling is- more or 
lefs perfect in proportion to the thinnefsof the epidermis; 
callofities in which weaken, and fometimes deftroy, both. 
Another ufe of the epidermis is, to regulate the cutane¬ 
ous evacuations already mentioned; the molt conliderable 
of which is infenlible tranfpiration. 
The laft univerfal integument of the human body, is 
-the membrana adipofa, or corpus adipofum. This is not, how¬ 
ever, a (ingle membrane, but a congeries of a great num¬ 
ber of membranous laminae, joined irregularly to each 
other at different diftances, fo as to form numerous inter¬ 
stices of different capacities, which communicate, with 
each other. Thefe interftices have been named celluUz, 
and the fubftance they compofe the cellularfubjlance. The 
thicknefs of the cellular fubftance is not the fame all over 
the body, and depends on the number of laminae of which 
it confifts. It adheres very clofely to the (kin ; runs in 
between the mufcles in general, and between their feveral 
fibres in particular; and communicates with the mem¬ 
branes which line the infide of the thorax and abdomen. 
This ftruCiure is demonftrated every day by butchers, in 
blowing up their meat when newly killed ; in doing which, 
/♦hey not only fwell the membrana adipofa, but the air in- 
iinuates itfelf likewife in the interftices of the mufcles, 
and penetrates even to the vifcera, producing a kind of 
artificial emphyfema. Thefe cellular interftices are fo ma¬ 
ny little bags or fatchels, filled with an undtuous or oily 
juice, more or lefs liquid, which is called fat; the diffe¬ 
rent confidence of which depends not only on that of the 
oily fubftance, but on the (ize, extent, and fub-divifion, of 
the cells. It is generally known, that the illullrious Mal- 
phigi took a great deal of pains about this fubftance; that 
jn birds and frogs, the vifcera and velfels of which are 
tranfparent, he thought he Caw a kind of duftus adipofi; 
and that,'by prefling thefe duifts, he obferved oily drops to 
run diftinttly into the fmall ramifications of the mefenterie 
veins; fttch duds, however, have not been feen by later 
anatomifts. 
The manufadure of foap, the compofition of fome of 
the ointments, and the different mixtures of oils with fa- 
line and acid liquors, give us fome idea, at leaft, of the for¬ 
mation of the fat in the human body ; but the organ which 
feparates it from the mafs of blood, which ought to be the 
iubjed of our prefent enquiry, is not yet fufftciently 
known. Fat is more fluid in living than in dead bodies. 
It melts with the heat of the fingers in handling it; and 
its fluidity is in part obftruded by the facculi which contain 
it. The method to take it entirely out of thefe bags is, 
to fet the whole over a fire in a proper veffel; for then 
the bags burft, and fwim in clufters in a true oily fluid. 
This fubftance increafes in quantity by reft and good li¬ 
ving; and, on the contrary, dimini (Ties by hard labour and 
a fpare diet. Why nourifhment fliould have this effed, 
js eafily conceived; and it is likewife eafy to fee, that an 
idle fedentary life mull render the fat lefs fluid, and con- 
fequently more liable to block the paflages of infenfible 
tranfpiration, through which it would otherwife run off. 
Hard labour diftolves it, and confequently fits it for paf- 
fing out of the body, with the other matter of infenfible 
tranfpiration. Some authors are of opinion, that it re¬ 
turns into the mafs of blood by the lymphatics; and that 
it can, for fome certain time, ftipply the want of nourifh¬ 
ment. By this, they think, the long abftinence of fome 
animals may be explained; but it would appear, that the 
The proportional differences, in the thicknefs of this 
membrana adipofa, are determined, and may be obferved, 
to be regular in fome parts of the body, where either 
beauty or ufe require it. Thus we find it in great quan¬ 
tities where the interftices of the mufcles would otherwife 
have left difagreeable hollow or void places ; but the (kin 
being filled, and as it were ftuffed with fat, is raifed, and 
an agreeable form given to the whole body. In fome parts 
of the body the fat ferves for a cufliion, pillow, or mat- 
rafs; as on the buttocks, where the laminae and cells are 
very numerous. In other parts, this membrane has few 
or no lamina;, and confequently little or no fat; as on the 
forehead, elbows, &c. In lome places it feems to be bra¬ 
ced down by a kind of natural contraction in form of a 
fold; as in that fold which feparates the bafis of the chin 
from the neck, and in that which diftinguiflies the buttocks 
from the reft of the thigh. We obferve it likewife to be 
entirely funk, or as it were perforated by a kind of dim¬ 
ple or foffula, as in the navel of fat perlons. Thefe de- 
preflions and folds are never obliterated, let the perfon be 
ever fo tat; becaufe they are natural, and depend on the 
particular conformation of the membrana adipofa, the la¬ 
minae ot which are wanting at thefe places. The fat is 
likewife of great ufe to the mufcles in preferving the flex¬ 
ibility neceffary for their actions, and in preventing or lef- 
fening their mutual frictions. Laftly, the fat, as a fine 
oily fubftance in its natural ftate, may be fome defence 
againft the cold, which we find makes more impreliion on 
lean than on fat perfons. It is for this reafon, that, to 
guard themfelves againft the exceilive colds of hard win¬ 
ters, and to prevent chilblains, travellers rub the extre¬ 
mities of their bodies, and efpecially their feet, with fpi- 
rituous oils, &c. This mafs of fat, which makes an uni- 
verfal integument of the body, is different from that which 
is found in the abdomen, thorax, canal of the fpinu dorli, 
articulations of the bones, and in the bones themfelves. 
But the difference of all thefe particular malfes of fat 
conlifts chiefly in the thicknefs or finenefsof the pellicles, 
in the largenefs or fmall nets of the cells, and in the con¬ 
fidence, fluidity, and l'ubtilty, of the oily matter. 
Some authors think the nails are productions of the cu¬ 
taneous papilla;; and others, that they are a continuation 
of the epidermis. This laft opinion agrees with experi¬ 
ments made by maceration; by means of which the epi¬ 
dermis may be feparated entire from the hands and feet, 
like a glove or lock. In this experiment we fee the nails 
part from the papillae, and go along with the epidermis, 
to which they remain united like a kind of appendix ; 
and yet their fubftance and ftruCture appears to be very 
different from that of the epidermis : but like it, they are 
alfo infenfible, and renewable after having been cut, or 
after having fallen off. Their fubftance is like that of 
horn, and they are compofed of feveral planes of longi¬ 
tudinal fibres foldered together. Thefe ftrata begin with 
a fquare root intermixed with the periofteum a little before 
the laft joints, and end at the extremity of each finger; 
they are nearly all of an equal thicknefs, but of different 
lengths. The external plane or ftratum is the longeft, 
and the reft decreafe gradually, the innermoft being the 
fhorteft; fo that the nail increafes in thicknefs from its 
union with the epidermis where it is thinneft, to the end 
of the finger where it is thickeft. The graduated extre¬ 
mities or roots of all the fibres of which thefe planes con- 
(ift, are hollowed for the reception of the fame number of 
very fmall oblique papilla;, which are continuations of 
the true (kin: which, having reached the root of the nail, 
forms a femilunar fold in which the root is lodged. After 
this femilunar fold, the (kin is continued on the whole in¬ 
ner furface of the nail, the papillae infinnating themfelves 
in the manner already faid. The fold of the (Tin is ac¬ 
companied by the epidermis to the root of the nail exte¬ 
riorly, to which it adheres very clofely. Three parts are 
generally 
