ACTION OF THE FEMALE. 709 



nerves. For in no other way can we account for many phenomena which 

 are obviously of a reflex character; such as the sudden contraction of the Ute- 

 rus, previously distended and inactive, when cold is applied to the external 

 surface of the body, or- when the child is applied to the nipple. In the first 

 stage of labour, the Uterine contractions appear to be alone concerned; and 

 it is not until the head of the child is passing through the Os Uteri, and is 

 entering the Vagina, that the assistance of the Expiratory muscles is called 

 in. The excitor fibres, which convey to the Spinal Cord the stimulus that 

 calls them into action, must originate, therefore, rather in the Vagina than in 

 the Uterus itself. Whilst the fibres of the fundus and body of the Uterus are 

 in powerful contraction, those of the Cervix Uteri and Vagina must be in a 

 state of dilatation ; and this dilatation appears to be in some respects different 

 from the mere yielding to the pressure of the child's head. A slow contrac- 

 tion of the fibres of the fundus and body of the Uterus, and a yielding of 

 those of the cervix, usually take place during some days previous to Par- 

 turition ; so that the child lies lower, and the size of the abdomen diminishes.* 



929. As to the reason why the period of Parturition should be just nine 

 months after that of Conception, we know nothing more than we do of that 

 of similar facts in the physical history of Man such as the periodical return 

 of the Catamenia, the renewal of the Teeth, the recurrence of the tend- 

 ency to Sleep, &c. That it is immediately dependent upon some state of the 

 constitution, rather than upon the condition of the Uterus, appears from the 

 fact that, in cases of Extra-uterine pregnancy, contractions resembling those 

 of labour take place in its walls. Moreover, various states of the constitu- 

 tion, especially that which is designated as irritability, may induce the occur- 

 rence of the parturient efforts at an earlier period ; and this constitutes Abor- 

 tion, or Premature delivery, according to the viability of the child. There 

 are some women, in whom this regularly happens at a certain month, so that it 

 seems to be an action natural to them ; but it is always to be prevented, if pos- 

 sible, being injurious alike to the mother and child ; and this prevention is to 

 be attempted by rest and tranquillity of mind and body, and by a careful avoid- 

 ance of all the exciting causes, which may produce Uterine contractions by 

 their operation on the Nervous system. For it is to be remembered that, 

 although the muscular fibres of the Uterus are capable, like those of the ali- 

 mentary canal, of an independent action, they are likely to be excited to ope- 

 ration through the Nervous system, and especially through the Sympathetic 

 ( 393). The same action which expels the Foetus, also detaches the Pla- 

 centa ; and if the Uterus contract with sufficient force after this has been 

 thrown off, the orifices of the vessels which communicated with it are so 

 effectually closed, that little or no hemorrhage takes place. If, however, the 

 Uterus does not contract, or relaxes after having contracted, a large amount 

 of blood may be lost in a short time from the open orifices. For some little 

 time after Parturition, a sero-sanguineous discharge, termed the Lochia, is 

 poured out from the Uterus ; and this commonly contains shreds of the De- 

 ciduous membrane, which had not been previously detached. Within a few 

 weeks after delivery, the Uterus regains (at least in a healthy subject) its pre- 

 vious condition; and it is probable that the portion of its mucous Membrane, 

 which had been thrown off" as Decidua, is very early reproduced. 



930. Although the duration of Pregnancy is commonly stated at nine 

 solar months, it would be more correct to fix the period at 40 weeks, or 280 

 days ; which exceeds nine months by from 5 to 7 days, according to the 

 months included. This, at least, is the average result of observation, in cases 



* See some interesting Papers on the Physiology of Parturition, by Dr. W. Tyler Smith, 

 in the Lancet, July 6 and 13, 1844. 



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