340 INNERVATION. [CHAP. XI. 



Certain conditions of the generative organs are dependent on the 

 spinal cord ; but they are developed only in a polar state of that 

 organ, usually present under sexual excitement. Erection of the 

 penis is evidently dependent on the cord in this way. In a state 

 of irritation of the cord, such as may be caused by traumatic injury, 

 erection or semi-erection is frequently present. In paraplegia there 

 is frequently an absence of the power. The excited state of the 

 Fallopian tubes in the female is attributable to the same cause. 

 The action of the uterus in parturition, and that of the bladder and 

 rectum when distended, is partly due to the stimulus of distension 

 on the muscular coats, and partly to the physical power of the cord 

 excited by the sensitive nerves of those organs. 



The nervous actions which accompany the nutritive functions 

 are of the physical kind, although not altogether removed from 

 the influence of volition and emotion, and have their centre in the 

 spinal cord. Thus, the heart is very liable to be influenced by 

 the spinal cord, and, no doubt, the blood-vessels are similarly re- 

 lated to 't ; and, through their influence upon the distribution of 

 blood to the various textures, it is plain that the state of the 

 spinal cord, or of parts of it, may readily affect the molecuh 

 changes in which nutrition and secretion intrinsically consist. This 

 subject will be further discussed when we come to consider tl 

 functions in question. 



It has been supposed, that the tone of the muscular system is 

 maintained by the spinal cord. If by tone be meant what we have 

 described as passive contraction, we can only remark, that the phe 

 nomena which characterize that state are just as obvious in muscl< 

 taken from animals recently deprived of the spinal cord as in others ; 

 and that the analogous state, rigor mortis, comes on as distinctly 

 when the spinal cord and brain have been removed, as if they wei 

 untouched. Healthy nutrition, in our opinion, supplies all the con- 

 ditions necessary for the maintenance of the tone or the passiv< 

 contraction ; nor is the spinal cord (although itself healthy) able 

 preserve the tense condition of the muscles, if they are not well 

 nourished. The removal of the spinal cord, indeed, immediately 

 produces a flaccid state of the muscles of the limbs ; but this is 

 owing to the immediate cessation of the slight degree of active 

 contraction necessary to maintain a certain posture. A decapitated 

 frog will continue in the sitting posture through the influence of 

 the spinal cord ; but immediately this organ is removed, the limbs 

 fall apart, from the loss of the controlling and co-ordinating influence 

 of the nervous centres. But careful examination will show, that in 



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