THE PLACENTA. 629 



It is also through the placental circulation that those disturbing 

 effects are produced upon the nutrition of the foetus, which result 

 from sudden shocks or injuries inflicted upon the mother. There is 

 now little room for doubt that various deformities and deficiencies of 

 the foetus, conformably to the popular belief, do really originate, in 

 certain cases, from nervous impressions, such as disgust, fear or anger, 

 experienced by the mother. The mode in which these effects may 

 be produced is readily understood from what has been said above 

 of the anatomy and functions of the placenta. We know very well 

 how easily nervous impressions will disturb the circulation in the 

 brain, the face, the lungs, &c. ; and the uterine circulation is quite 

 as readily influenced by similar causes, as physicians see every day 

 in cases of amenorrhoea, menorrhagia, &c. If a nervous shock may 

 excite premature contraction in the muscular fibres of the pregnant 

 uterus and produce abortion, as not unfrequently happens, it is cer- 

 tainly capable of disturbing the course of the circulation through 

 the same organ. But the foetal circulation is dependent, to a great 

 extent, on the maternal. Since the two sets of vessels are so closely 

 entwined in the placenta, and since the foetal blood has here much 

 the same relation to the maternal, that the blood in the pulmonary 

 capillaries has to the air in the air- vesicles, it will be liable to de- 

 rangement from similar causes. If the circulation of air through 

 the pulmonary tubes be suspended, that of the blood through 

 the general capillaries is disturbed also. In the same way, what- 

 ever arrests or disturbs the circulation through the vessels of the 

 maternal uterus must necessarily be liable to interfere with that 

 in the foetal capillaries forming part of the placenta. And lastly, 

 as the nutrition of the foetus is provided for wholly by the placenta, 

 it will of course suffer immediately from any such disturbance of 

 the placental circulation. These effects may be manifested either 

 in the general atrophy and death of the foetus ; or, if the disturbing 

 cause be slight, in the atrophy or imperfect development of par- 

 ticular parts ; just as, in the adult, a morbid cause operating through 

 the entire system, may be first or even exclusively manifested in 

 some particular organ, which is more sensitive to its influence than 

 other parts. 



The placenta must accordingly be regarded as an organ which 

 performs, during intra-uterine life, offices similar to those of the 

 lungs and the intestine after birth. It absorbs nourishment, reno- 

 vates the blood, and discharges by exhalation various excrementi- 

 tious matters, which originate in the processes of foetal nutrition. 



