UTERUS (FUNCTIONS). 



force, for it is beyond question a healthy ne- 

 cessity which, for the purpose of advancing 

 the process, demands this graduated change 

 of the uterine rythm throughout labour. 

 Rythm plainly does not, like peristaltic action, 

 depend upon the structure of the organ which 

 displays it, for the three examples here taken, 

 viz., respiratory muscles, heart, and uterus, 

 differ from each other materially in composi- 

 tion. The first consists of striated voluntary 

 fibre ; the second of striated involuntary fibre; 

 the third of unstriated involuntary fibre. It 

 may therefore be concluded, that something 

 else than structure determines rythm. This 

 appears to depend rather upon the manner in 

 which the contractions are evoked, and hence 

 upon the mode of innervation, which is dif- 

 ferent for each organ. The heart and respi- 

 ratory muscles each admit of more easy ob- 

 servation than the uterus, and referring to 

 them for aid in the elucidation of this ques- 

 tion, we find that each of these organs, or 

 sets of organs, is provided with a nervous 

 rythmic centre, upon which its rythm depends, 

 and upon the injury or destruction of which 

 the rythm immediately ceases, the rythmic 

 centre of respiration being in the medulla ob- 

 longata, and that of the heart in its own pro- 

 per ganglia. Which of these divisions of the 

 nervous system furnishes the rythmic centres 

 of the uterus has not been determined, but 

 from the analogies just quoted, we may select 

 by preference the heart, because its actions 

 most nearly resemble those of the uterus, 

 in being purely involuntary, while the case 

 of the respiratory muscles constitutes an ex- 

 ample of mixed movements wherein volitional 

 can be superadded to unconscious rythmic 

 motion. 



If therefore the rythmic action of the uterus 

 is regulated in like manner with that of the 

 heart, we must, upon the strength of this 

 analogy, look for its rythmic centres among 

 the sympathetic ganglia which lie nearest to 

 the organ. 



And this view does not necessarily exclude 

 a certain influence of the spinal nerves over 

 the rythmic action of the uterus. For just 

 as under emotion or bodily excitement both 

 the cardiac and respiratory rythms are accele- 

 rated, so, as labour advances, and more parts 

 become irritated, the uterus appears to receive 

 an addition of nerve force which may be pos- 

 sibly acquired from other and more distant 

 centres than its own proper ganglia. 



The heart's rythmic centres have been re- 

 garded by some physiologists as so many 

 " magazines " of nerve-force, whence at regu- 

 lated intervals this force is discharged, causing 

 the muscular structure to contract in accord- 

 ance with the rate of supply of the stimulus. 

 The influence of these nerve-centres is best 

 shown by placing a ligature upon them, or by 

 cutting them away. When hindered in their 

 operation by tying, the rythm ceases, though 

 the motor power is not lost. When they are 

 cut away, together with certain portions of 

 the heart, the other portions cease to have 

 rythmic motion, though they may still be 



675 



artificially excited to repeated single ac- 

 tions.* 



But an inconstant stimulus thus furnished 

 to the muscular structure being powerless to 

 produce a permanent or tonic contraction, the 

 effect after a short time passes away to be 

 reproduced upon a fresh application of the 

 excitement. In this way rythm, so far as it 

 is dependent upon nervous supply, is ap- 

 parently determined. 



But in the case of the uterus we observe 

 that the rate of the rythm must be to a cer- 

 tain extent limited by the peculiar nature of 

 the uterine fibre. For this, as already shown, 

 is of a kind which cannot be excited to rapidly 

 repeated action like the heart. In this form 

 of fibre the response to the stimulus is slow, 

 and often does not take place until after the 

 excitant is withdrawn. Hence the meaning 

 of that slow repetition of uterine action which 

 is observed in ordinary labour. 



When this point is further examined, it will 

 be found that, according to the degree or kind 

 of excitement employed, the uterine rythm 

 may be merely accelerated, or a r)thmic may 

 be converted into a more continuous action. 

 The influence of the passage of the child 

 during labour over successive surfaces in 

 quickening uterine action has been already 

 shown. Another example may be drawn from 

 the effects of ergot. When ergot is given by 

 the stomach some time usually elapses before 

 the ergotine mixes with the blood sufficiently 

 to excite the rythmic centres, but that being 

 done, the action is simply augmented, or else 

 occasionally it becomes so violent that the in- 

 tervals are obliterated, and one contraction 

 becomes merged in another, so that an inter- 

 mittent is converted into a continuous uterine 

 action. 



But that which more certainly demonstrates 

 that the rate of the motions, whether rythmic 

 or constant, is dependent on the kind and ex- 

 tent of irritation, is the variation in the results 

 obtained by different modes of inducing pre- 

 mature labour. If, according to the method 

 of Kiwisch, water is injected simply against 

 the cervix, after several repetitions, rythmic 

 action is slowly excited. If the cervix is dis- 

 tended by the introduction of a sponge tent, 

 rythmic action ensues more quickly and cer- 

 tainly. But if the first proceeding is so varied 

 that the water, instead of being merely thrown 

 against the cervix, is introduced between the 

 membranes and the uterine walls for a very 

 short distance, so as gently to effect their sepa- 

 ration from the inner surface of the uterus, 

 labour is induced with greater certainty and 

 speed than in any other way ; but should the 

 separation be carried still further, some such 

 tumultuous form of labour results as ergot pro- 

 duces when acting in the manner just specified. 

 The uterus acting continuously and very ener- 

 getically rather than intermittingly. 



Influence of the different nervous centres upon 

 the uterus in parturition. In the present un- 

 settled state of neural physiology, especially in 



* Paget, Croonian Lecture ; Proceedings of Roy. 

 Soc. vol. viii. No. xxvi. 1857. 



x x 3 



