ANATOMY IN A NUTSHELL. 429 



nerves are indigenous in every part of the spinal cord. The branches that pass 

 to the femoral artery from the Anterior Crural and Obturator are gray rami 

 communicantes, and through these branches the non-medullated axis-cylinder 

 processes of the sympathetic ganglion cells reach the vessels, fascia', bones, 

 cartilages, and periosteum of the lower extremity. 



A gray ramus communicans passes to the tibia from the branch of the in- 

 ternal popliteal nerve which passes to the Popliteus muscle. Each spinal nerve 

 is joined near its origin by a gray ramus communicans from the sympathetic 

 gangliated cord. The superior cervical ganglion gives off four gray rami com- 

 municantes to the first four cervical nerves. These rami may come from the 

 sympathetic nerve below the ganglion. The middle cervical ganglion s< ntds two 

 gray rami to the fifth and sixth cervical nerves. The inferior cervical ganglion 

 sends two gray rami to the seventh and eighth nerves. The first dorsal ganglion 

 (stellatum) of the sympathetic or the last cervical sends a gray ramus to the first 

 dorsal nerve. One ganglion may send gray rami to two nerves, or two gray 

 rami to one nerve. In the lumbar and sacral regions the gray rami are long and 

 pass downward and outwards over the bodies of the vertebrae to reach the an- 

 terior division of the nerve. In the lumbar region they pass under the Psoas 

 magnus muscle. 



The white rami communicantes originate in the motor roots of the cranial 

 and spinal nerves. Some of these white rami pass through the vertebral gang- 

 lia without interruption, while others arborize with cells in the vertebral gang- 

 lia. The white rami communicantes are indigenous in the thoracic and upper 

 lumbar regions only, while the gray rami are indigenous in all parts of the cord. 

 The white rami may be called the visceral divisions of the spinal nerves. Al- 

 though the white rami are for the most part derived from the ventral or an- 

 terior roots, yet some of them come from the dorsal or posterior roots. The 

 white rami from the hist two lumbar, and peihaps also from the third and fourth 

 lumbar nerves, pass forward by themselves or in company with the gray rami 

 to join the upper pait of the lumbar gangliated cord. The fifth lumbar and in si 

 sacral do not have white rami while the third sacral and possibly tin s ( cond and 

 fourth have both white and gray rami. The fifth sacral and coccygeal nerves 

 hav< no white rami. 



In Plate CXCVI1 1 we s< e the gray and white rami communicantes. A, B, ( '. 

 and D represent white or n < dullat< d rami, while E, F, G, H, L, M, N, r< pres< nt 

 tlu gray or non-medullated ran i. A passes from the anterior or ventral root 

 to the sympathetic ganglion of its own segmenl through which it passes to the 

 ganglion below. B has a similar origin but ends in the ganglion of its own 

 segment. Chas a similar origin and passes through the sympathetic ganglion 

 of its own segment to a prev< rtebral plexus or directly to visc< ra. 1 ) has a sim- 

 ilar origin and passes through the sympathetic ganglion of its own stum, nt to 

 end in a higher ganglion. F originates in the sympathetic ganglion and passes 

 along the posterior nerve rod to the dura mater of thi mn\. G originates in 

 the sympathetic ganglion and passes along the posterior division of the spinal 

 nerve to its destination. II originates in the sympathetic ganglion ami passes 

 along the anterior division of the spinal nerve t<> iis destination. It passes to 



