910 OF GENERATION ACTION OF THE FEMALE. 



without such assistance. The earliest period at which this may occur, will 

 be presently considered ( 764). 1 



760. At the conclusion of about forty weeks, or (less correctly) nine solar 

 months, 2 from the period of conception, the time of Parturition arrives. In 

 this act, the muscular walls of the Uterus are primarily concerned ; for a 

 kind of peristaltic contraction takes place in them, the tendency of which 

 is to press the contents of the cavity from the fundus towards the os uteri, 

 and finally to expel them ; and this contraction is alone sufficient to empty 

 the uterus, when no impediment is presented to the exit of the foetus, as we 

 see in the occasional occurrence of post-mortem parturition. It is, in fact, 

 in the contraction of the fibres of the fundus and body of the uterus, and 

 in a relaxation of those about the cervix (which relaxation is something 

 quite different from a mere yielding to pressure, and is obviously a vital 

 phenomenon that marks a peculiarity in the actions of this part), that the 

 first stage of an ordinary labor essentially consists. 3 There is no proof 

 whatever that these changes are dependent upon nervous influence ; in fact, 

 there is much evidence that the parturient action of the uterus is not the 

 result (as some have maintained it to be) of a "reflex" action of the Spinal 

 Cord, but is due to its inherent contractility ; for numerous instances have 

 occurred in which normal parturition has taken place, notwithstanding the 

 destruction of the lower part of the Cord, or the existence of a state of com- 

 plete paraplegia which marked its functional inactivity; and the contin- 

 uance of the peristaltic action for some time after somatic death, when 

 neither the Cerebro-spinal nor the Sympathetic system can afford any sup- 

 ply of nervous power, is a yet more satisfactory proof of the same position. 4 

 Nevertheless, it seems quite certain that muscular contractions of the 

 Uterus may be induced by reflex action ; for in no other way can we account 

 for numerous phenomena, which distinctly mark the operation of remote 

 causes acting through the nervous system ; such as the induction of uterine 



1 A case recorded by Dr. J. R. Beck (Med. and Surir. Reporter, 1872, No. l~>i, 

 seems to show that the Uterus may participate rather actively in the process of im- 

 pregnation. a.s he observed the os uteri to open and close with considerable energy 

 on mechanical stimulation. Oser and Schlesinger (Strieker's Med. Jahrb., 1872) 

 have shown that powerful contractions of the uterus are produced by the circulation 

 of dyspnoeic arterial blood, partly owing to excitation of some centre for the uterine 

 nerves existing 1 in the cranium, and partly owing to irritation of excitable tU.-ue in 

 the uterus itself; and Schlesinger has further shown (Strieker's Med Jahrb., 1873, 

 p. 1 ) that uterine contractions can also be induced by electric excitation of the centric 

 extremity of a divided dorsal nerve. (For other experiments on the reflex contrac- 

 tion of the uterus after irritation of sensory nerves, see Spiegel berg, Zeits. f. rat. 

 Med , 8 R , Bd. ii, 1858, and Korner, Studien des Phys. Inst. zu Breslau, Heft iii, 

 and Obermeier, Pamphlet, Bonn, 1865.) Scanzoni found that irritation of the nip- 

 ples, which, according to Luschka, contain so many tactile and Pacinian corpuscles, 

 causes contraction of the uterus. The nerve-plexus on the aorta is an important but 

 not the only channel for the conduction of these motor impulses. 



2 Although " nine months " is usually spoken of as the term of Gestation, yet the 

 real term of forty weeks exceeds this by from five to seven days, according to the 

 months included. The mode of reckoning customary among women, is to dale from 

 the middle! of the month after the last appearanceof the Catamcnia: but it is certain 

 that Conception is much more likely to take place soon after they have ceased Inflow, 

 or even just before their access, than in the intervening period (g 741); so that, in 

 nio.-t instances, it would be most correct to expect labor at forty weeks and a few 

 day> alter the last recurrence of the menses. The period of Quickening may be re- 

 lied on in some women, in whom it occurs with great regularity in a certain week of 

 pregnancy ; but in general there is great latitude as to the time of its occurrence. 

 The usual or average time seems to be about the eighteenth week of gestation 



3 See a paper corroborating ttiis statement, by Arthur Scott Dunkin, M.D , in 

 Edinb. Med. Journal, vol. ii, 18(551, p. 523. 



* See cases recorded in Lancet, 1872, vol. i, pp. 517, 596. 



