762 



THE NERVOUS SYSTEM. 



lumbar spinal nerves, and it contains, as well, inedullated fibres continued down 

 from the lower part of the thoracic sympathetic trunk, and derived from the 

 visceral branches (white rami communicantes) of the lower thoracic nerves. 



This part of the trunk is characterised by great irregularity in the number of 

 the ganglia. They are usually four in number, but there are frequently more 

 (up to eight) ; and in extreme cases fusion may occur to such an extent that the 



separation of individual ganglia 

 s - becomes impossible. 



1. Central Communicating 

 Branches. White rami communi- 

 cantes. Only the first two (or 

 three) lumbar spinal nerves send 

 visceral branches (white rami 

 communicantes) to the upper 

 lumbar ganglia or to the sym- 

 pathetic trunk. These nerves form 

 the lower limit of the thoracic- 

 lumbar visceral branches of the 



2 spinal nerves. They comprise vaso- 

 motor fibres (for the genital organs), 

 and motor fibres for the bladder 

 and uterus. 



Gray rami communicantes pass 

 from the gangliated trunk to the 

 anterior rami of the lumbar nerves 

 in an irregular manner. One 

 ramus may divide so as to supply 

 branches to two adjacent spinal 

 nerves ; or one spinal nerve may 

 be joined by several (two to five) 

 gray rami from the sympathetic 

 trunk. 



The rami course deep to the 

 origin of the psoas major muscle 

 and over the bodies of the vertebras. 

 Gray rami sometimes pierce the 

 fibres of the psoas muscle. 



2. Peripheral Branches of 



no. 640.-THE LUMBAR PORTION OF THE SYMPATHETIC Distribution. -From the lumbar 

 GANGLIATED TRUNK AND LUMBAR PLEXUS. (From a dissection.) Sympathetic trunk numbers 



T.n, T.12, L.I, L.2, L.3, L.4, L.5, Anterior rami of spinal small branches arise irregularly, 



nerves, with white and gray rami communicantes. and Supply the abdominal aorta, 



Sy, Sympathetic trunk ; Va, Vagus nerve ; G.S, Greater reinforcing the aortic plexus (de- 

 splanchnic nerve, joining coeliac ganglion ; S.R.C, Supra- r i v ed from the CCeliaC plexus), 

 renal gland and plexus ; R.P1, Renal plexus ; Ao.Pl, 

 Aortic plexus ; S. M, Superior mesenteric plexus ; I.M, 

 Inferior mesenteric plexus ; Hy.Pl, Hypogastric plexus ; 

 Q, Nerves to quadratus lumborum ; I.H, Ilio-hypogastric 

 nerve ; I.I, Ilio - inguinal nerve ; G.C, Genito - femoral 

 nerve ; E.C, Lateral cutaneous nerve ; A.C, Femoral 

 nerve ; Ace. Obt, Accessory obturator nerve ; Obt, 

 Obturator nerve ; 4, 5, Lumbo-sacral trunk. 



r . PARS PELVINA SYS- 

 TEMATIS SYMPATHICI. 



The pelvic part of the sym- 

 pathetic trunk, like the cervical 

 and lower abdominal portions of 

 this system, receives no white rami communicantes from the spinal nerves. The 

 visceral branches (pelvic splanchnic} of the third sacral nerve, and usually, also, 

 the second or fourth sacral nerve, enter the plevic plexus without being directly 

 connected with the sympathetic trunk. These nerves, however, are to be regarded 

 as homologous with the white rami communicantes of the thoracico- lumbar 

 nerves (abdominal splanchnic}. They convey to the pelvic viscera (1) motor 

 and inhibitory fibres for rectum, uterus, and bladder, (2) vaso-dilator fibres for the 

 genital organs, and (3) secretory fibres for the prostate gland. 



