REFLEX ACTIONS. MOVEMENTS OF GENITAL ORGANS, ETC. 305 



discomfort. On the other hand, if the stimulus is deficient, the will must 

 aid the expulsors, in order to overcome that resistance which is due to the 

 reflex contraction of the sphincters; of this also we may convince ourselves, 

 when a sense of propriety, or a prospective regard to convenience, occasions 

 us to evacuate the contents of the rectum or bladder without a natural call to 

 do so. 



393. Movements of the Genital Organs. The muscular contractions in- 

 volved in the Emissio Seminis are clearly of a reflex nature ; being inde- 

 pendent 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 Degluti- 

 tion) by a particular local irritation. That this irritation need not amount to 

 a sensation, is proved by cases already referred to ( 372) ; 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 further appears, from 

 the experiments of Valentin, that the Spinal Cord may operate on the Genital 

 organs through the Sympathetic system. Contractions were excited in the 

 vas deferens vesiculae 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 lumbar 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, abdominal muscles, &c., are called into 

 action (as in defecation) through the Spinal Cord ; but that the contractions 

 of the Uterus itself are but little dependent on its connection 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 information. 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 foetus 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 ordinarily have to en- 

 counter ; since the tension of all the muscles surrounding the outlet would be 

 destroyed, by the cessation of the activity of the Spinal system of nerves 

 ( 398). 



394. Protecting Agency of the Spinal Cord. 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 loathing. There is 

 another protective influence exerted by it, of a still more remarkable nature. 

 It has been ascertained by Dr. M. Hall that, if the functions of the Brain be 

 suspended or destroyed, without injury to the Spinal system of nerves, the 



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