THE GREAT SYMPATEETIC NERVOUS SYSTEM. 781 



The terminal hranch of the sacral plexus forms the great sciatic nerve whose 

 distribution la the same as that of Carnivova. The collateral ramuscules of the great 

 sciatic are the branch of the long portion of the biceps; the semitendinosus and 

 semimembranosus branoli ; the branch to the great adductor ; and, lastly, that to the 

 short portion of the bicep3. It terminates by the external and internal popliteal 



The mmcalo-cutaneous and anterior tibial, continuations of th« external popliteiis 

 comport themselves almost the same as in the Dog. Thi-y form dorsal collaterals to the 

 third, fourth, and fifth toes, as well as to the second. 



The imteraaipopi/feo! presents an external saphenous nerve that passes along the 

 external border ot the foot, and has, in addition, a branch that ascends on the dorsum 

 of that organ, rhe external saphenous furnishes the dorsal collaterals to the first toe, 

 and the external collateral to the second. The posterior tibial nerve continues the 

 internal sciatic in the leg ; it terminates in the plantar nerves. The internal plantar 

 furnishes the collateral nerves to the fifth, fourth, and third toes, and the internal 

 collateral of the second toe. The external divides into three branches: the two 

 superficial branches form the collaterals of the first toe, and the external collateral of the 

 second; the deep branch passes inwards, behind the interosseous muscles, and is 

 expended in those of the fourth space, after, giving filaments to the oblique abductor of 

 the large toe, transverse abductor, last two lumbricales, to tlie interosseous, and very 

 fine filaments to the articulations of the tarsus with the metatarsus. 



It will therefore be seen that, in Man, the branches of the deep trunk of the 

 external plantar join those of the internal plantar, to form the collateral nerves. 



CHAPTER III. 



THE GBEAT SYMPATHETIC NEEVODS SYSTEM. 



Peeparation of the Great Sympathetic. — The same subject ought to suffice for the 

 preparation of this, as well as the pneumogastric and spinal nerves. After placing the 

 animal in the first position, the intestines are removed, one of the posterior limbs cut 

 off, and the greater portion of the os innominatum cleared away by sawing through the 

 symphysis pubis and the neck of the ilium ; the dissection of all the abdomino-pelvio 

 portion of the system, and that of the terminal branches of the pneumogastric nerve, is 

 then proceeded with. The anterior limb of the same side should be afterwards 

 detached, the scapula having been previously sawn across its middle part, and the 

 thorax thrown open by the ablation of the entire costal wall, in sawing through the 

 sternal cartilages below, and the ribs above, at their superior extremity All the 

 thoracic portion of the ganglionic nervous apparatus, and the pneumogastsric nerves 

 may then be prepared. Nothing more remains to be accomplished except the dissection 

 of the sympathetic and the vagus nerve in the cervico-cephalic region, with that of the 

 spinal nerve ; this operation is not attended with any diflSoulty, and should be preceded 

 by the extirpation of a branch of the inferior maxilla. It is useful to inject the arteries 

 previously ; as then the filaments of the sympathetic thiit lie alongside the vessels 

 ot the different organs in the abdominal cavity can be more easily followed. 



The great sympathetic, also named the trisplanchnij system (a-n-Xavxvov 



an intestine or viscus), because of its position and destination, is the nervous 



apparatus of the organs of vegetative life. 



As has been already shown in the general consideration of the nerves 

 and the whole nervous system, this apparatus has for its base two long cords 

 extending from the head to the tail, underneath the vertebral column, and to 

 the right and left of the median line. Towards the last sacral vertebra, a 

 portion of these two cords converge towards each other, and lie beside the 

 median coccygeal artery. Some anatomists think that the great sympa- 

 thetic does not stop at this point, but is prolonged beneath the coccygeal 

 vertebra, where it enters a ganglion that has been described of late years 

 as the " coccygeal gland," and whose nature has been very much contested. 



Bach cord presents on its course numerous ganglia, to whose presence it 



