CENTERS IX THE SPINAL CORD. 735 



After division of the spinal cord Goltz observed that the anal sphincter con- 

 tracted rhythmically about a finger introduced into the rectum. The coordinated 

 activity of the center is, therefore, possible only through connection with the 

 cerebrum. After extirpation of the lumbar cord, the anal sphincter at first loses 

 its tone, although this is partially restored later. The muscle does not degenerate; 

 perhaps its trophic center is situated in the mesenteric ganglion. 



The center for micturition. Budge's vesicospinal center, for the sphinc- 

 ter muscle is situated at the level of the fifth (dog) or the seventh (rabbit) 

 lumbar vertebra, for the muscular wall of the bladder at a somewhat 

 higher level. It functionates in a coordinated manner only when con- 

 nected with the cerebrum (see p. 522). 



The center for erection is situated in the lumbar portion of the cord. 

 The centripetal fibers are the sensory nerves of the penis. The centrif- 

 ugal fibers are, for the deep artery of the penis, the vasodilator nerves 

 from the first, second and third sacral nerves (Eckhard's erector nerves), 

 for the ischiocavernosus and the deep transverse perineal muscle the 

 motor fibers from the third and fourth sacral nerves. The latter may 

 be stimulated also voluntarily, the former also in part from the cerebrum 

 by directing attention to sexual activity. Eckhard observed erection 

 also after stimulation of higher portions of the spinal cord (Landois 

 likewise in man), as well as of the pons and the cerebral peduncles. 



In accordance with clinical observations the centers for the bladder and the 

 rectum and for erection are situated at the point of exit of the first, second, third 

 and fourth sacral nerves. 



The center for ejaculation. The sensory (dorsal nerve of the penis) 

 are the exciting nerves. The center (Budge's genitospinal center) is 

 situated at the level of the fourth lumbar vertebra, in rabbits. The 

 motor fibers of the vasa deferentia are derived from the fourth and fifth 

 lumbar nerves, which enter the sympathetic and finally pass thence to 

 the vasa deferentia. The motor fibers for the bulbocavernous muscle, 

 the ejaculator of the seminal fluid from the bulb of the urethra, are 

 contained in the third and fourth sacral nerves (perineal nerves). Ejac- 

 ulation may be induced by mechanical stimulation of the lumbar cord, 

 in guinea-pigs. 



The center for the act of parturition is situated at the level of the first 

 and second lumbar vertebrae. The centripetal fibers are derived from 

 the uterine plexus, into which also the motor fibers from the spinal cord 

 again enter. Goltz and Freusberg observed impregnation and delivery 

 in a bitch with the spinal cord divided at the level of the first lumbar 

 vertebra. Similar results have been observed in women with the spinal 

 cord divided. Normal birth occurred with subsequent involution of the 

 uterus and secretion of milk. 



Centers for the vascular nerves, both vasomotor and vasodilator, are 

 distributed throughout the entire spinal axis. Among these is to be 

 included also the center for the spleen, which is situated between the 

 first and fourth cervical vertebrae, in the dog. They can be excited 

 reflexly, although they are subordinated to the dominating centers in 

 the medulla oblongata. They may be influenced also by psychic stimu- 

 lation, from the cerebrum. 



Centers for the secretion of sweat have perhaps a distribution analogous 

 to that of the centers for the vascular nerves. 



The movements excited from the centers named are, in accordance with what 

 has been stated, to be designated coordinated reflexes and fundamentally to be 



