ANATOMY. 



brachial artery to the elbow, and then ra- 

 mifying under the skin of thej inner side 

 of the fore-arm. 



5. Cutaneus externus, distributed along 

 the outer side of the fore-arm. 



6. Median nerve, a large trunk accom- 

 panying the brachial artery, then pro- 

 ceeding 'to the hand, and supplying the 

 thumb, with the two neighbouring fingers, 

 and the radial side of the ring finger. 



7. Radial nerve, bends round the os 

 luimeri, from the inner to the outer side 

 of the bone ; it is distributed superficially 

 to the back of the hand and fingers. 



8. Ulnar nerve, accompanying the nerve 

 of the same name to the hand, where it 

 supplies the little finger, and the ulnar 

 side of the ring finger. 



The twelve pairs of dorsal nerves sup- 

 ply the muscles in their neighbourhood. 

 They give'' also numerous branches of 

 communication to the great sympathetic. 



The five pairs of lumbar nerves send 

 branches to the neighbouring muscles, and 

 give communicating filaments to the great 

 sympathetic. They also produce two 

 nerves distributed to the front of the 

 thigh ; viz. the anterior crural, which 

 g-ots out of the pelvis near the external 

 iliac artery, and has an extensive distribu- 

 tion to the thigh and leg ; and the obtu- 

 rator nerve, which belongs also to mus- 

 cles on the front of the thigh. 



The sacral nerves give communicating 

 branches to the great sympathetic, and 

 several filaments to the organs of gene- 

 ration in both sexes, to the bladder, rec- 

 tum, &.c. They mostly, however, unite to 

 form the great sciatic. nerve, which is the 

 largest trunk in the body. It goes out of 

 the pelvis at the back part, and passes to 

 the thigh. Here it sometimes is pressed 

 by the weight of the body in sitting, and 

 causes the effect of the foot going to 

 sleep, as it is expressed in common lan- 

 guage. Tliis nerve is distributed to the 

 back of the thigh, and over the whole leg 

 and foot. 



Great sympathetic or intercostal nerve. 

 It is first formed by a small filament of 

 the .6th pair, or nervus motor externus, 

 together with another derived from the 

 pterygoid branch of the superior maxil- 

 lary- In the upper part of the neck this 

 nerve has a very large ganglion lying on 

 the vertebrx, called the superior cervicaj 

 ganglion. This ganglion receives branche s 

 of communication from the five upper u 

 pairs of cervical nerves, and sends oflf 

 branch to the heart. The trunk descend 

 along the neck, and forms an interior cer- 

 vical ganglion, which has communicating 



filaments from the neighbouring spinal 

 nerves, and sends several branches to the 

 heart, forming the cardiac plexus. The 

 sympathetic nerve then passes through 

 the chest, over the heads of the ribs, re- 

 ceiving branches from each dorsal nerve, 

 and forming a dorsal ganglion between 

 every two vertebrae. In its course it sends 

 off the splanchnic nerves, which go 

 through the diaphragm, and form a vast 

 and most intimate plexus about the root 

 of the cueliac artery, called the cxliac 

 plexus, from which the liver, pancreas, 

 spleen, large and small intestines, and 

 kidnics, derive their nerves. All these 

 organs receive several filaments, united 

 so as to form plexuses, and surrounding 

 their arterial trunks. 



The trunk of the great sympathetic en- 

 ters the abdomen, and goes over the lum- 

 bar vertebra, receiving branches of com- 

 munication, and forming lumbar ganglia; 

 it is then continued along the front of the 

 sacrum, where the sacral nerves supply 

 communicating filaments, and where five 

 sacral ganglia are formed. 



OllGANS OF SENSE. 



Organ of vision. The globe of the eye 

 is contained in a bony socket, formed by 

 the bones of the cranium and of the face. 

 It is furnished with muscles which can 

 move it in every direction, and surround- 

 ed by a very soft and delicate kind of fat, 

 which yields to it in all its motions. It is 

 composed of certain membranes, called its 

 tunics or coats, and of other parts, termed 

 humours. 



Its figure is very nearly spherical ; but 

 the transparent portion in front is the sec- 

 tion of a smaller sphere than the globe. 

 The optic nerve, to which the eye-ball is 

 attached posteriorly, enters considerably 

 on the inside of the axis of the eye. 



The coats of the eye are disposed con- 

 centrically ; and the exterior,which is very 

 dense, firm, and tough, is called the scle- 

 rotica. This does not cover the whole 

 globe, but leaves a circular opening iu 

 front, filled by the transparent cornea, 

 which, although pellucid, is a very firm 

 and strong membrane. Hence, the sclero- 

 ticu and cornea together form a very com- 

 plete exterior case, which defends and 

 supports the more delicate parts within. 

 The necessity of having the front of the 

 globe transparent, for the purpose of ad- 

 mitting 1 the rays of light, is obvious. 



Under tne scleroticaa soft and vascular 

 membrane surrounds the eye-ball, and is 

 called the choroid coat. It is connected 



