CH. XLVII.] VISCERAL REFLEXES 677 



impulses do not rise into consciousness, and even on injury pain is 

 often absent. In disease where they are stirred up to excessive 

 action, as in various forms of colic, the pain, however, may be intense. 

 A good deal of pain is usually " referred " to skin areas which are 

 " tender," and Ross's suggestion that the pain in such cases is referred 

 to parts supplied by sensory cutaneous fibres ending in the same 

 segments of the cord as do the afferent fibres from the viscera in 

 question, has been amplified and placed beyond doubt by Head's 

 researches. 



Bladder Reflexes. The spinal region which acts as the micturition centre is 

 that with which the first, second, and third lumbar, and the second, third, and fourth 

 sacral roots are connected. Transverse section of the cord about the level of the 

 sixth lumbar segment (in cat and rabbit) causes immediate escape of urine from the 

 bladder. In the first days after the operation the bladder can only be emptied 

 by artificial stimulation, and especially easily by a light quick pressure on the dis- 

 tended bladder through the abdominal walls. It is not the pressure that squeezes 

 out the urine, it merely sets going a reflex in which contraction of the detrusor and 

 relaxation of the sphincter constitute the final stage. Later on the urine is voided 

 ** spontaneously" at intervals, and this is usually accompanied by defaecation. 



Goltz and Ewald found in dogs in which the lower part of the cord had been 

 totally removed, that the bladder emptied itself spontaneously from time to time 

 months later, but usually the bladder had to be emptied by artificial means. In 

 man retention of urine is* a common and usually a permanent symptom after a total 

 transverse lesion of the cord. 



Defaecation. A regular expulsion of faecal matter occurs without difficulty in 

 animals after transverse section of the cord in the upper lumbar region. The tone of 

 the external sphincter is generally recovered a few minutes after the operation ; and 

 in Goltz and Ewald's dogs the tonus returned even when the lower part of the cord 

 was entirely removed. After a total transverse lesion of the cord in man, incontin- 

 ence of faeces is usually described, but this is not the case in monkeys. Gowers 

 describes two states in disease which can be distinguished by introducing the finger 

 into the rectum : (1) if the centre is inactive a momentary contraction caused by local 

 irritation of the sphincter is followed by permanent relaxation ; (2) relaxation is 

 followed by gentle tonic contraction : in such cases the reflex centre and its nerves 

 are intact. 



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 

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

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

 breast. 



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

 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. 



