494 On Auxiliary Forces concerned in the Circulation [Apr. 24 y 



is suddenly emptied, as immediately after delivery in woman, this 

 resistance is at the lowest, consequently the effect of descent of the 

 diaphragm on the circulation is but slight, compared with that 

 state which obtains when the parietes are in a high state of health, 

 and the intestines are fully distended with gas, &c. 



It must be evident that the amount of blood contained in the 

 vessels within the abdomen must vary much, according to the tension 

 of the parietes ; but this matter does not belong to the subject of this 

 note. 



III. " Note on the Auxiliary Forces concerned in the Circulation 

 of the Pregnant Uterus and its Contents in Woman." By 

 J. Braxton Hicks, M.D., F.R.S., F.L.S., &c. Received 

 March 26, 1879. 



Whatever view we may take of the structure of the placenta, it is 

 generally admitted that both in the large sinuses in the walls of the 

 pregnant uterus, and also in the decidual processes in the placenta as 

 well as in the intervillal spaces the motion of the fluids can be but 

 very slow, that is, if the circulation wholly depended upon the maternal 

 cardiac impulse. 



However, in 1871,* I pointed out a fact which had not been before 

 observed, that the uterus was in the habit normally of alternately re- 

 laxing and contracting every five, ten, or twenty minutes during the 

 whole of the pregnancy from the earliest period, at least from the 

 second month, and not as had before been believed only under irrita- 

 tion, and towards the end of gestation. This movement is doubtless 

 homologous with the peristaltic movements in the uteri of the lower 

 animals. 



In that paper I pointed out — 1st, that these movements of the uterus 

 provide for the frequent movement of the blood in the uterine sinuses 

 and the decidual processes ; and, 2ndly, that they facilitate the move- 

 ment of the fluid in the intervillal space of the placenta, or in that 

 which has been called the placenta sinuses, and I remarked, " What- 

 ever view we may hold of the structure of the placenta, whether on 

 the one hand there be blood amongst the villi in maternal sinuses, or 

 on the other merely a serous fluid, in any case it is through one or 

 the other medium the villi absorb the material for the aeration of the 

 foetal blood ; and there can be no doubt that from its position it must 

 be in a more or less stagnant state. It is not difficult, therefore, to 

 recognise the effect which the change in the solidity and shape must 

 produce on the fluids in the placenta, as well as in the uterine walls. 



* " Obst. Trans. Lond.," vol. xii. " On the Contractions of the Uterus during 

 Pregnancy : their Physiological Effects and Value in the Diagnosis of Pregnancy." 



