6 3 6 ANATOMY 
and the courfe of them from the neck to the arm may 
teach us how much better effects veficatories, of Itimii'a- 
ting nervous medicines, would have, when applied to the 
fkin covering the tranfverfe proceffes of the vertebrae of 
the neck, or at the axilla, than when they are put be¬ 
tween the (boulders, or upon the fpina! procefles, in con- 
vulfions or palfles of the fuperior extremities, where a 
ftimiilus is required. 
The twelve dorfal nerves of each fide, as foon as they 
efcape from between the vertebrae, lend a branch forward 
4 o join the intercoftal, by which a communication is made 
among them all; and they foon likewife give branches 
backward to the mufcles that raife the trunk of the body, 
their principal trunk being extended outwards to come at 
the furrow in the lower edge of each rib, in which they 
run toward the anterior part of the thorax, between the 
internal and external intercoftal mufcles, giving oft' branch¬ 
es in their courfe to the mufcles and integuments of the 
thorax. The fix lower dorfal nerves give branches to the 
diaphragm and abdominal mufcles. May not the commu- 
nications.of all thefe nerves be one reafon, why the parts 
they ferve aft fo uniformly and conjanftly in refpiration, 
and c'onfpire together in the convulftve motions of cough¬ 
ing, fneezing, &c. The twitching fpafms that happen 
iometimes in different parts of the mufcles of the abdo¬ 
men, by an irritation on the branches of the lower dor¬ 
fal nerves, are in danger of occafioning a miftake in prac¬ 
tice, by their refemblance to the cholic, nephritis, &c. 
The communications of thefe lower ones with the inter- 
coftalsj may ferve to explain the violent effort of the ab¬ 
dominal mufcles in a tenelinus, and in child-bearing. 
The five lumbar nerves on each fide communicate with 
the intercoftal and with each other, and give branches 
backwards to the loins. Branches of tire lecond, third, 
and fourth, make up one trunk, which runs along tire 
fore-part of the pelvis; and is fpent on the adduftor 
mufcles, and on the integuments on the infide of the 
thigh. This nerve is called tire obturator, or pofierior cru¬ 
ral nerve ._ Whoever attends to the courfe of thefe lum¬ 
bar nerves, and of the fpermatic veflels and nerves upon 
the pfoas nmfcle, with the oblique palfage of the ureter 
over that niufcle, will not be furprifed, that when a (tone 
is palling in this canalj or even when it is inflamed, the 
trunk of the body cannot be raifed ereft, without great 
pain; or that the fkin-of the thigh becomes lefs fenfible, 
and the thigh is drawn forward, and that the tefticle of¬ 
ten fvvells and is drawn convulftveiy towards the ring of 
the abdominal mufcles. 
The fix pair of the falfe vertebrae conftft each of fmall 
pofterior branches fent to the hips, and of large anterior 
branches. The firft, lecond, and third, after coming 
through the three upper holes in the fore-part of the os 
facrum, join together with the fourth and fifth of the 
loins, to form the largeft nerve of the body, which is 
well known by the name of fciatic or ifchiatic nerve. This, 
after lending large nerves to the different parts of the 
peivis, and to the external parts of generation and the 
podex, as alfo to the mulcles of the hips, paffes down to 
the bone of the thigh at its back-part, giving oft' nerves 
to the neighbouring mufcles and integuments. A little 
above the ham, where it has the name of poplitceus nervus, 
it fends off a large branch that paffes over the fibula, and, 
linking among the mufcles on the anterior external part of 
the leg, runs down to the foot, to be loft in the upper 
part of the larger toes, fupplying the neighbouring muf¬ 
cles and integuments eyery where in its palfage. By at¬ 
tending to the particular diftribution of the nerves of the 
inferior extremities, we may fee why people with fraftu- 
red legs, efpecially where there are fplinters, fhould be 
fubjeft to convulftve flattings of the fraftured member : 
Why, upon tying the blood-veffels in an amputation of 
the leg, the patients fhould fometimes complain of vio¬ 
lent pain in their toes; why fuch patients fhould alfo be 
troubled with ftartings ; why, for a conliderable time af¬ 
ter the amputation of the difeafed limb, when the fup- 
puration is well advanced, they fhould complain of pain 
in the fore which occaiioned the amputation. 
1'he branches of the four laft cervical nerves, and erf 
the firft dorfai, which are bellowed on the fuperior extre¬ 
mities, and the two crurals, with the fciatic, which are 
diftnbuted to the inferior extremities, are much larger 
proportionally to the parts they ferve, than the nerves of 
the trunk of the body, and efpecially of tire vifeera; and 
for a very good reafon, that in tire molt common necefiary 
actions of life, a fufficient quantity of fluid, on which 
the influence of nerves feems to depen i, may befupplied 
to the mufcles there, which are obliged to perform more 
frequent and violent contractions than thole of any other 
parts. The fize of the nerves of the inferior extremities 
feems larger proportionally than in the fuperior extremi¬ 
ties; the inferior extremities having the weight of the 
whole body to fuftain, and that frequently at a great dif- 
advantage. What tire effeft of the nerves here being in¬ 
jured is, we fee daily. When people happen, by lifting 
wrong, to comprefs the fciatic nerve, they are incapable 
for fome time after to fupport themfelves on the affefted 
extremity; and this is ftill more remarkable in the feia- 
tica or hip-gout, in winch the member is not only weak¬ 
ened, but gradually Ihrivels and waftes. 
The Nerves of the Human Body are reprefented in 
tb.e Anatomical Plate iX. of which the following is an 
explanation, viz. 
FRONT VIEW. 
r, The firft branch of the fifth pair of nerves. 2, The 
fecond branch of the fifth pair. 3, The third branch of 
the fifth pair. 4, The trunk of the eighth, pair cut. 5, 
The recurrent nerve. 6, The great fympathetic nerve. 
7, The uppermoft ganglion of the great fympathetic nerve. 
8, The ramus fplanchnicus of the great fympathetic nerve. 
9, A branch of the fub-occipital, or tenth pair of the 
head, joining with the great fympathetic nerve. 10, The 
firft cervical nerve. 11; The feventh cervical nerve: the 
intermediate cervicals come out in a fimilar manner. 12, 
The phrenic nerve. 13, The axillary plexus. 14, The 
mufcular nerve of the,arm. 15, The articular nerve, 
j6, The fpiral nerve. 17, The radial nerve.' 18, The 
ulnar nerve. 19, The firft intercoftal nerve. 20, The laft 
intercoftal nerve : the other ten come out in the lame man¬ 
ner. 21, The firft lumbar nerve. 22, The laft lumbar 
nerve : the three intermediate lumbar nerves come out in 
a fimilar way. 23, Branches from the external thoracic 
nerves running down upon the fide of the thorax. 24, 
Branches fent off from the intercoftal and lumbar nerves 
to fupplv the outer part of the thorax and abdomen. 25, 
Nerves of the os facrum. 26, The obturator nerve. 27, 
The anterior crural nerve. 28, A branch of the anterior 
crural nerve, which runs near the vena faphena major. 
29, The anterior tibial nerve running down to the foot. 
BA CK VIEW. 
1, The recurrent nerve. 2, A branch of the fourth 
cervical nerve, joining the recurrent one before it termi¬ 
nates on the mufculus trapezius. 3, Branches of the fifth 
pair, perforating the fcaletuis medius to be fpent upon the 
rhomboid mufcles. 4, Branches of the fub-occipital 
nerve, running to the fmall mufcles at the under and back 
part of the head. 5, Pofterior branches of the cervical 
nerves. 6, Pofterior branches of the dorfal nerves. 7, 
Pofterior branches of the dorfal and lumbar nerves run¬ 
ning to the ereftor mufcles of the back. 8, Pofterior 
branches of the dorfal nerves, penetrating the intercoftal 
mufcles.' 9, Branches from the laft dorfal, and from the 
lumbar nerves,, fupplying the lumbar and abdominal muf¬ 
cles. 10, Branches from Tome of the lower cervical nerves, 
running to the mufcles on the back-part of the fcapula. 
11, The articular nerve. 12, A branch from the axillary 
plexus running to the mufculus latiflimus dorli. 13, Ano¬ 
ther branch from the axillary plexus running to the latif- 
fimus dorfi and feiratus inagnue. 14, The fpiral nerve. 
15, The 
