CH. XLIX.] VISCERAL REFLEXES 721 



Spinal Visceral Reflexes. 



The spinal grey matter contains centres which regulate the 

 operation of many involuntary muscles. Some of these centres are : 



The cilio-spinal centre controls the dilatation of the pupil ; it is 

 situated in the lower cervical region, reaching as far down as the 

 origin of the first to the third thoracic nerve. 



Subsidiary vaso-motor centres. The principal vaso-motor centre 

 is situated in the bulb, and subsidiary centres are scattered through 

 the spinal grey matter (see p. 302). 



The same is probably true for all the muscular viscera, but 

 particular study has been directed to those in the pelvis, and centres 

 for micturition, defcecation, erection, and parturition are contained in 

 the lumbo-sacral region of the cord. If the spinal cord is cut through 

 above the situation of these centres, the result is in general terms 

 that any influence of the higher (voluntary) centres over these 

 actions is no longer possible. The actions in question are then 

 simply reflex ones occurring unconsciously at certain intervals, and 

 set in movement by the peripheral stimulus (fulness of bladder, or of 

 rectum, etc.). If the portion of the cord where these centres are 

 placed is entirely destroyed, the result is paralysis of the muscles 

 concerned, though in certain cases, even after such a severe injury, 

 some amount of recovery has been noticed, which must be attributed 

 to the peripheral ganglia being able to play the part of reflex centres. 



The phenomena of micturition (p. 580), and defaecation (p. 562) 

 have, however, already been described at length, arid it only remains 

 to add a few words concerning two other reflexes in which the 

 generative organs are concerned. 



Uterine Reflexes. Uterine contractions can be induced by rectal injections, 

 the passage of a foreign body into the uterus, the application of the child to the 

 breast, and by other means. In animals faradisation of the central end of the first 

 sacral nerve produces the same result. The contractions of the uterus are therefore 

 reflex. Several cases have been recorded in which parturition has occurred normally 

 in women who have had the cord divided across completely in the thoracic region ; 

 it is thus evident the centre must be a lumbar one. In such cases the uterine con- 

 tractions technically called " pains" are strong, but pain is, of course, absent. The 

 communication with the lumbar region appears to be principally by the first three 

 lumbar nerves. Similar observations have been made experimentally in animals, and 

 in one of Goltz and Ewald's dogs in which the cord had been removed from the lower 

 thoracic region downwards, pregnancy followed coitus, and terminated with success- 

 ful parturition. The mammary glands enlarge as usual in such cases, even when, as 

 iq Routh's well-known case (where the cord was completely destroyed at the seventh 

 thoracic segment), there can be no nervous communication between the pelvis and 

 the breast. 



Erection. This can be excited in man even immediately after a transverse 

 lesion of the cord ; so also can ejaculation, but not so commonly. The evidence 

 in favour of such acts being spinal reflexes is very complete in the case of animals. 



2 Z 



