THE SYMPATHETIC NERVES 685 



I T. All the small muscles of the hand and fingers. 



I-XII T. Muscles of the back. 



I-XI T. Intercostal muscles. 



VIT-XII T. Abdominal muscles. 



I L. Lowermost parts of the abdominal muscles; quadratus lumborum. 



II L. Cremaster. 



III L. Psoas ; sartorius ; iliacus minor ; pectineus ; adductors of the thigh. 



IV L. Quadriceps femoris; gracilis; obturator externus (?). 



V L, Gluteus medius and minimus; tensor fasciaB femoris; semitendi- 



nosus; semimembranosus ; biceps. 

 I S. Pyriformis; obturator internus; gemelli; quadratus femoris; 



gluteus maximus; long extensors of the foot and toes; pero- 



neus longus and brevis. 

 II S. Long flexors of the foot and toes; large calf muscles; small foot 



muscles. 



III S. Ejaculator muscles; muscles of the perineum. 



IV S. Sphincter and detrusor muscles of the bladder; sphincter ani. 

 V S. Levator ani. 



The same must be said of this summary that was said of the sensory nerves, 

 namely, that a given muscle is supplied by more than one spinal root. Accord- 

 ingly the data given here indicate the central regions of distribution, or. the 

 other way about, the chief nerve supply for the separate muscles. Starr finds, 

 for example, that the scaleni muscles are innervated by the second and third 

 cervical roots, the diaphragm by the third and fourth, the deltoid by the 

 fourth and fifth, the biceps by the fifth and sixth cervical, the sartorius by 

 the first and second lumbar, the quadriceps femoris by the second and third, 

 the adductors of the thigh by the third and fourth, etc. 



It was formerly asserted by Preyer and Krause that the skin covering any 

 given muscle is supplied with sensory fibers by the same spinal nerve as that 

 which supplies the underlying muscle with motor fibers. Sherrington finds, 

 however, that this is not the case; for certain displacements occur causing the 

 skin region to be situated farther distally than the corresponding muscle. The 

 flexor sides of the thigh and fore leg and the extensor side of the arm appear 

 to be the only exceptions to this rule. The different sensory fibers of the 

 muscles themselves appear to belong to the same segment as the motor fibers. 



3. THE SYMPATHETIC NERVES 



A. RELATIONS OF THE SYMPATHETIC NERVES TO THE CENTRAL 



NERVOUS SYSTEM 



The nerve fibers traversing the sympathetic nerves are both afferent and 

 efferent in function ; and they mediate a great variety of functions not under 

 direct influence of the will. To these belong the vasoconstrictor and vaso- 

 dilator nerves, accelerator nerves of the heart, motor and inhibitory nerves 

 of the stomach, intestine, bladder, etc. They constitute therefore the greater 

 part of the visceral nerves. It is justifiable to enumerate along with the com- 

 ponents just named the visceral fibers contained in certain cranial nerves 

 and those arising from the sacral roots. Doing this, we can then say, that 



