PROTECTING AGENCY OF THE SPINAL CORD. 153 



of the Sympathetic, or the roots of the superior abdominal Spinal nerves ; and 

 that strong contractions of the bladder are excited, by irritation of the inferior 

 portion of the abdominal Sympathetic, but especially of its sacral portion, and 

 of the roots of the middle and inferior abdominal nerves of the Spine. In these, 

 as in former cases, no effect is produced by irritation of the Spinal Nerves, 

 unless the portion of the Sympathetic connected with the particular organ 

 be entire. 



203. The influence of the Spinal Cord on the Genital organs is of a simi- 

 lar character. The muscular contractions involved in the Emissio Seminis 

 are clearly of a reflex nature ; being independent of the will, and not capable 

 of restraint by it, when once fully excited ; and being producible in no other 

 way, than (like those concerned in Deglutition) by a particular local irritation. 

 That this irritation need not amount to a sensation, is proved by the cases 

 already referred to ( 182) ; and it has been also shown by experiment, that 

 section of the Spinal Cord in the lumbar region does not prevent the act from 

 being performed, the lower division only being concerned in the reflexion of 

 the impression. It appears, also, from the experiments of Valentin, that the 

 Spinal Cord may operate on the Genital organs through the Sympathetic sys- 

 tem. Contractions were excited in the vas deferens and vesiculse seminales, 

 especially of the Guinea Pig at the time of heat, by irritation of the inferior 

 lumbar and highest sacral portions of the Sympathetic ; and the Fallopian 

 tubes, as well as the Uterus itself, may be excited to contraction, by irritation 

 of the same nerves as those which excite the rectum, namely, the lower lum- 

 bar and first sacral nerves of the Spine. This last fact is important, in regard 

 to the rationale of the operation of certain medicines, such as aloes, which are 

 known to have an influence on both parts. In regard to the act of Parturition, 

 there would seem reason to believe, from the evidence of cases of paraplegia, 

 that, of the muscles whose operation is associated in it, the diaphragm, abdomi- 

 nal muscles, &c., are called into action (as in Defecation) through the Spinal 

 Cord ; but that the contractions of the Uterus itself are independent of all con- 

 nection with the nervous centres. Of the reason why the muscles, which 

 were up to that time inert, should then combine in this extraordinary manner, 

 and with such remarkable energy, Physiology can afford no certain informa- 

 tion. There can be little doubt, however, that the stimulus usually originates 

 in the uterus, or in some of the neighbouring organs which are incommoded 

 by the pressure ; but it may also result from some condition of the general 

 system, in which the uterus itself is but little concerned. It is an interesting 

 fact, which has been more than once observed, that the fetus may be expelled 

 from the dying body of the mother, even after the respiratory movements have 

 ceased. This would appear due to the contraction of the Uterine fibres alone, 

 which, like those of the heart and alimentary canal, retain their irritability 

 longer than those of the muscles supplied by the cerebro-spinal nerves ; and 

 the power of these would be unopposed by the resistance which they ordina- 

 rily have to encounter ; since the tone of all the muscles surrounding the outlet 

 would be destroyed by the cessation of the activity of the Spinal system of 

 nerves ( 207). 



*' XL Protecting Agency of the Spinal Cord. 



204. From the foregoing details it appears, that one of the chief functions 

 of the Spinal Cord is to control the orifices of the various open cavities of the 

 body ; and this function evidently has safety, as well as convenience, in view. 

 It has been manifestly designed by the All-wise Creator, .that the glottis should 

 close against agents injurious to the organs within ; and that the effort to vomit 

 should be excited, by the attempt to swallow substances so nauseous as to induce 



