URINAR Y BLADDER. 



849 



more and more preponderant directive influence over those "reflexions," those 

 expressions of the creature's neural states, its " doings." The relative slight- 

 ness of the " visceral " part of spinal shock in higher animals indicates the 

 extent to which the reactions of the visceral musculature and some of the 

 reactions of the skeletal musculature accessory thereto are normally uncon- 

 nected with higher conscient nervous organs. 



SPINAL VISCERAL KEFLEXES. 



To the viscera belong three sets of peripheral afferent channels (1) 

 the vagus ; (2) the spinal roots from first thoracic to second lumbar 

 inclusive ; (3) the second, third, and fourth sacral roots. The trophism 

 of these channels depends on the vagal ganglia and the spinal ganglia 

 mentioned. The efferent channels to the viscera lie in three correspond- 

 ing sets. 



The viscera are insentient under numerous traumatic and other 

 injuries ; in disease they nevertheless may cause pain. Much of this 

 pain is " referred " to areas of the body surface, where the skin is then 

 often found to be " tender," i.e. hyperalgesic. James Eoss 1 suggested 

 that the pain is in such cases referred to parts supplied by sensory 

 cutaneous nerve fibres ending in the same segments of the cord as do the 

 afferent fibres of the viscus diseased. Head has examined the data for 

 this hypothesis, and has established and elaborated it. 2 The following 

 conspectus of Head's results states the probable distribution of visceral 

 afferent fibres of the spinal ganglia in man : 



Heart, . . First, second, and third thor- 

 acic. 



Lungs, . First, second, third, fourth, 



and fifth thoracic. 



Stomach, . Sixth, seventh, eighth, and 

 ninth thoracic. 



Intestines, . Ninth, tenth, eleventh, and 

 twelfth thoracic. 



Liver and gall Seventh, eighth, ninth, and 

 bladder, tenth thoracic. 



Kidney and Tenth, eleventh, twelfth 

 ureter, thoracic and first lumbar. 



Bladder, . Second, third, and fourth 

 sacral, and eleventh and 

 twelfth thoracic and first 

 lumbar. 



Prostate, . Tenth, eleventh (and twelfth) 

 thoracic, and first, second, 

 and third sacral. 



Testis and Tenth, eleventh, twelfth 

 epididymis, thoracic and first lumbar. 



Ovary, . . Tenth thoracic, ovarian ap- 

 pendages, eleventh and 

 twelfth thoracic and first 

 lumbar. 



Uterus, . Tenth, eleventh, twelfth 

 thoracic, first lumbar, 

 second, third, and fourth 

 sacral. 



Rectum, . Second, third, and fourth 

 sacral. 



Urinary bladder. The region of the cord from which efferent and to 

 which afferent channels belonging to the urinary bladder pass is twofold, a 

 sacral with which the second, third, and fourth sacral roots (man), and a lumbar 

 with which the first, second, and third lumbar roots are connected. From this 

 region, when isolated, reflex contractions and relaxations of the detrusor and 

 sphincter can be elicited. The intravesical pressure which the sphincter with- 

 stands is lowered 3 by spinal transection between the fifth and sixth lumbar 

 segments of the cat (between sixth and seventh in rabbit). 



These can therefore be said to form a spinal vesical centre. The upper 

 limit of the region lies near the hindmost level of the origin of the second 



1 "On the Segmental Distribution of Sensory Disorders," Brain, London, 1887, vol. x. 

 p. 333 ; cf. further, Dana, New York Med. Journ., 1887. 



2 Brain, London, 1893, vol. xvi. ; 1894, vol. xvii. p. 339. 



3 Masius, Bull. Acad. roy. d. sc. de Belg., Bruxelles, 1868 ; Kupressow, Arch. f. d. 

 ges. Physwl.,Eonn, 1872, Bd. v. S. 292; Ott, Journ. PhysioL, Cambridge and London, 

 1880, vol. ii. p. 60. 



VOL. ii. 54 



