116 Royal Society. 



to perfect the tables of the moon is a desideratum in physical astro- 

 nomy. 



The author has obtained numerical results in the first approxima- 

 tion ; the value of the variation agrees within a few seconds with the 

 result of Newton in the third volume of the Principia. 



The next paper was entitled, " On the Tides," by the same. 



This paper contains tables of the results of observations made at 

 Brest, with regard to the principal inequality of the tides, or that 

 which is independent of the parallaxes and declinations of the moon 

 and sun, and depends solely on the moon's age, that is, on the time 

 of her passage through the plane of the meridian ; from which it ap- 

 pears that the tables of the tides for London are not applicable to 

 Brest, by merely changing the establishment, that is, by adding a con- 

 stant quantity, as has been hitherto supposed ; and the same remark 

 applies to any distant parts. 



The third paper was entitled, " On the Structure of the Human 

 Placenta and its connection with the Uterus." By Robert Lee, M.D. 

 F.R.S. Physician to the British Lying-in Hospital. 



In the year 1780 Mr. John Hunter presented a paper to the Royal 

 Society, in which he laid claim to the discovery of the true structure 

 of the placenta, and of its vascular connections with the uterus. From 

 the appearances which he observed in a preparation of the gravid 

 uterus, after both the veins and arteries had been injected, and a lon- 

 gitudinal incision made through the anterior parietes of the uterus 

 where the placenta adhered to its internal surface, he was led to con- 

 clude that the arteries which are not immediately employed in con- 

 veying nourishment to the uterus go on towards the placenta, and 

 proceeding obliquely between it and the uterus, pass through the 

 decidua without ramifying ; and that just before entering the placenta, 

 after making two or three spiral turns, they open at once into its 

 spongy substance. The corresponding veins he represents as com- 

 mencing from the spongy substance of the placenta by wide mouths, 

 and after passing obliquely through the decidua, entering the sub- 

 stance of the uterus and immediately communicating with the proper 

 veins of that organ. Dr. Wm. Hunter's description of the same 

 vessels accords with that of his brother. He regards the placenta as 

 consisting of two distinct parts, namely, an umbilical portion which 

 belongs to the foetus, and a uterine portion which belongs to the 

 mother, each having its peculiar system of arteries and veins ; and he 

 supposes that while, in the foetal portion, the arteries and veins form 

 continuous canals, these two sets of vessels communicate, in the 

 uterine portion, by the intervention of cells, into which the arteries 

 terminate, and from which the veins begin. 



The subject was afterwards investigated by Noortwych, Roederer, 

 and Haller, but without any satisfactory result ; and the doctrines 

 laid down by the Hunters were generally acquiesced in by subsequent 

 anatomists. 



The author of the present paper having had opportunities of exa- 

 mining six gravid uteri, and many placentae expelled in natural 

 labour, finds reason to conclude that no cellular structure, such as 



that 



