176 



ANATOMY AND PHrSIOLOGY OF 



minor, and shoulder joint, and ends in the 

 insertion of the levator humeri. 



The subscapular nerves run upward be- 

 tween the shoulder and chest, and enter the 

 subscapularis. 



The spiral or external cutaneous nerve is 

 furnished by the axillary plexus ; arises be- 

 hind the humeral artery, and passes between 

 the OS humeri and the head of the triceps, 

 through the extensors, to the external flexors 

 of the canon. It gives off several branches 

 to the triceps, ramifies on the fore and out- 

 ward part of the knee, and sends branches 

 to the heads of the extensor muscles. 



The radial nerve descends with the 

 humeral artery to the inward side of the 

 elbow joint, and runs along the back part 

 of the radius to the knee ; passing under 

 the annular ligament, it descends to the leg, 

 and takes the name of the internal metacar- 

 pal ners'e. It gives off numerous tvv^igs to 

 the muscles, and finally becomes subcutane- 

 ous. 



The ulnar nerve originates from the 

 humeral plexus. It passes down the radius, 

 under the annular ligament, to the tendo 

 perforans, and there becomes the external 

 metacarpal nerve. It gives off internal 

 cutaneous and subcutaneous branches, rami- 

 fies into cellular substance, penetrates the 

 heads of the flexors, and finally disperses 

 its ramifications in front of the leg. 



The metacarpal nerves continue down 

 the leg, over the fetlock joint, where they 

 become the plantar nerves ; these pm'sue 

 their course behind their corresponding 

 blood-vessels to the back part of the foot, 

 which they penetrate to the inner ■ side of 

 the lateral cartilages. 



The plantar nerve detaches a branch from 

 the fetlock to the lateral cartilage ; another 

 passes to the fatty frog. The final branch 

 enters a hole in the back and lower part of 

 the coffin bone, in company with the plan- 

 tar artery, and there divides and distributes 

 its ultimate branches around the edges of 

 the sole. 



NERVES OF THE HIND EXTREMITY. 



The crural nerve is derived partly from 



the second, third, fourth, and fifth lumbar 

 nerves. It makes its appearance under the 

 transverse process of the loins, and proceeds 

 in a line with the external iliac artery. It 

 gives off filaments to the psoas magnus, 

 iliacus, rectus, and vastus internus muscles. 

 It also gives off cutaneous filaments ; one 

 runs to the stifle, and ends in ramifications 

 upon the fore part of the thigh. The other 

 continues down the leg, and can be traced 

 as low as the fetlock. » 



The obturator nerve, contributed to by 

 third and fourth lumbar nerves, sweeps 

 round the brim of the pelvis, and detaches 

 twigs to the obturator muscles. Its ultimate 

 filaments are expended on the triceps and 

 gracilis. 



The gluteal nerve, after leaving the cavity 

 of the pelvis, accompanies the gluteal artery, 

 and passes into the substance of the gluteal 

 muscles. 



The sciatic nerve derives its origin from 

 the sacral and last of the lumbar nerves ; 

 after leaving the cavity of the pelvis, passes 

 between the Mp joint and the tuberosity of 

 the ischium, and plunges into the substance 

 of the haunch. Here it divides into branches 

 called the popliteal nerves. At the hock its 

 principal branch separates into the external 

 and internal metatarsal nerves ; the former 

 runs over the flexor pedis to the os calcis. 

 Their subsequent com*se and ultimate dis- 

 tribution are the same as those of the plan- 

 tar nerves of the fore extremity. The second 

 popliteal nerve passes between the bellies 

 of the gastrocnemii, above the first, detach- 

 ing twigs to them in its passage, and then 

 spreads into many branches, which pene- 

 trate the heads of the flexor muscles of the 

 foot, and send filaments into the stifle joint. 



SYMPATHETIC NERVE. 



This nerve derives its name from the uni- 

 versal influence which it has on the nervous 

 system. It communicates with the head, 

 neck, chest, pelvis, and abdomen, by its fre- 

 quent intercourse and connection with their 

 respective nerves. It is supposed by some 

 writers to be a nervous system of itself. 

 It has, at different distances, a great uumber 



