Royal Society. 117 



that described by Dr. Hunter, exists in the human placenta^ and that 

 there is no connection between this organ and the uterus by great 

 arteries and veins. He thinks himself warranted in concluding that 

 the placenta does not consist of two portions, maternal and foetal, 

 but that the whole of the blood sent to the uterus by the spermatic 

 and hypogastric arteries, except the small portion supplied to its pa- 

 rietes and to the membrana decidua by the inner membrane of the 

 uterus, flows into the uterine veins or sinuses j and, after circulating 

 through them, is returned into the general circulation of the mother 

 by the spermatic and hypogastric veins, without entering the sub- 

 stance of the placenta. Such have been the results of the author's 

 own examinations of the structure of the gravid uterus, both when 

 injected and uninjected ; and also of an examination of the prepara- 

 tions of that organ, contained in the Hunterian Museum at Glasgow, 

 made at his request by Dr. Nimmo. These views are also corrobo- 

 rated by the careful examination by the author of a preparation of 

 the uterus with the placenta adhering to its inner .surface, in the 

 Museum of the Royal College of Surgeons of London, which is sup- 

 posed to have been put up by Mr. Hunter himself nearly fifty years 

 ago. The cellular structure of the placenta has been too hastily in- 

 ferred from the masses of wax found interspersed in its substance, 

 after the vessels have been injected ; but this appearance the author 

 ascribes wholly to extravasation in consequence of rupture of the 

 vessels. 



Nov. 24. — A paper was read, entitled, " Facts adduced in refuta- 

 tion of the assertion that the Female Ornithorhynchus Paradoxus has 

 Mammae." By SirEverard Home, Bart. F.R.S. 



The author, after a minute examination, in which he was assisted 

 by Mr. Hartshorn and Mr. Bauer, of three specimens of female orni- 

 thorhynchi sent to him by Governor Darling, could not discover 

 rnammae, although these parts are represented as existing by Professor 

 Meckel. 



A paper was next read, entitled, " On an Inequality of long Period 

 in the Motions of the Earth and Venus." By George Biddell Airy, 

 A.M. Plumian Professor of Astronomy and Experimental Philosophy 

 in the University of Cambridge. 



The author had pointed out, in a paper published in the Philo- 

 sophical Transactions for 1828, on the corrections of the elements of 

 Delambre's Solar Tables, that the comparison of the corrections of 

 the epochs of the sun and the sun's perigee, given by the late obser- 

 vations, with the corrections given by the observations of the last 

 century, appears to indicate the existence of some inequality not in- 

 cluded in the arguments oftho.se tables *. As it was necessary, there- 

 fore, to seek for some inequality of long period, he commenced an 

 examination of the mean motions of the planets, with the view of 

 discovering one whose ratio to the mean motion of the earth could be 

 expressed very nearly by a proportion of which the terms .are small. 

 The appearances of Venus are found to recur in very nearly the same 



• See Phil. Mag. and Annals, N.S., vol. iii. p. 128. 



order 



