PROCEEDINGS

OF THE

ROYAL SOCIETY OF EDINBURGH.

1843.

No. 22.

Monday, 6th February 1843.

Sir T. MAKDOUGALL BRISBANE, Bart., President, in the Chair.

The following communications were read :—

1. On the Law of Visible Position in Single and Binocular Vision, and on the representation of Solid Figures by the Union of dissimilar Plane Pictures on the Retina. By Sir David Brewster, K.H.,-concluded.

This subject is treated under eight different heads :—1. On the law of visible direction in Monocular vision. 2. On the law of visible direction in Binocular vision. 3. On vision of objects of three dimensions, by monocular vision; by binocular vision. 4. On the binocular vision of figures of different magnitudes. 5. On the cause of the perception of objects in relief by the coalescence of dissimilar pictures. 6. On the doctrine of corresponding points. 7. On the vision of cameos and intaglios. 8. On the change in the apparent position of the drawings of solid bodies.

The general object of this paper is to establish the law of visible direction, (position in monocular vision,) and to shew that it is equally applicable to binocular vision, and affords a complete explanation of various phenomena which had been considered incompatible with

it, but for which no theory had been proposed. In the last two sections, the author treats of the collateral subject of the vision of cameos, and of the drawings of solid bodies.

2. Papers on Glaciers. No. 1, Account of a Geometrical Survey of the Mer de Glace of Chamouni. By Professor Forbes.

This paper does not admit of abridgment. The author gave an account of a survey which he executed of the whole extent of the principal glacier of Mont Blanc and its tributaries. A base line of nearly 3000 feet was carefully measured in the valley, and extended by means of a very careful triangulation to a point on the glacier distant 28,600 feet, and elevated 4400 above the base line. From the several points of this triangulation, the positions and heights of the adjoining mountains were taken and laid down on a map on a scale of 3 of nature, portions having been drawn out to 1oooo. The map was laid before the Society, and is now being engraved.

The following Donations of Books to the Society's Library were announced.

Elements of Chemistry, including the Applications of the Science to the Arts. By Professor Graham, University College, London. Part 6. By the Author.

Maps of the Irish Ordnance Survey, containing the County of Waterford, in 42 sheets.-By his Excellency the Lord Lieutenant.

The following Donations to the Museum were presented— Specimens of Volcanic Rocks from Vesuvius, and Minerals from Derbyshire.-Presented by Sir T. M. Brisbane, Bart. Specimens of Fossil Shells from Grignon, collected by Dr Stark in Oct. 1833.-Presented by John Stark, Esq.

The following gentlemen were duly elected Ordinary Fellows of the Society :

Dr John Rose Cormack, Fellow of the College of Physicians of Edinburgh.

Dr Allen Thomson, Professor of the Institutes of Medicine in the University of Edinburgh.

Monday, 20th February 1843.

The Right Honourable Lord GREENOCK, Vice-President, in the Chair.

The following communications were read :

1. On the Anatomy of the Human Placenta. By John Goodsir, Esq., Conservator of the Museum of the Royal College of Surgeons of Edinburgh.

In the first section of the paper, the author described the parts which enter into the structure of the villi of the placenta. The villi are covered by a membrane with which anatomists are already familiar. Within this membrane, and attached to its internal surface, is a layer of cells, which has also been observed, and described as epithelium. The cells composing this layer, Mr Goodsir denominated the external cells of the villus. The next structure is a membrane not hitherto described, and named by the author the internal membrane of the villus. The adhesion of this membrane to the external cells is so slight, that it is generally seen at some distance from them, even in villi which have undergone no violence. Within the internal membrane of the villus, a set of very transparent cells, hitherto undescribed, is situated. These the author denominated the internal cells of the villus. The ultimate loops of the umbilical capillaries are imbedded in this mass of cells, the cells and vessels being closely bound up by the internal membrane of the villus.

The second section of the paper was devoted to the description of the foetal portion of the organ. Mr Goodsir described the development and structure of the tufts of the chorion. He stated that the development consists in the addition of cells to the extremity of each villus of the tuft, these being supplied by a germinating mass, which resembles the spongiole of the root-fibre of a plant. These tufts and villi are entirely cellular, and are covered by a fine membrane. Before the villi become vascular, the ovum derives nourishment from the decidua, by the absorbing agency of the cells of the spongioles at the extremities of the villi of its chorion. When bloodvessels have formed in the villi, the cells, although less numerous, still remain, and are believed by Mr Goodsir to be the active absorbing agents in the villi of the placenta. In the perfect placenta, the villi of the chorion appear as the internal membrane, and the internal cells described in the first part of the paper. These, along with the umbilical vessels, constitute the fœtal portion of the placenta.

In the third section of the paper, in which Mr Goodsir treated of the maternal portion of the organ, he corroborated the statements of of Professors Weber and Sharpey as to the nature and structure of the decidua; and he more particularly described an interfollicular tissue, consisting of cells, which conduces, he thinks, as much as the enlargement of the glands, to the thickening of the mucous membrane. Since the discovery made by Professors Weber and Sharpey, too little attention, he believed, has been directed to the secretions of the thickened mucous membrane. This secretion, which forms the greater part of the decidua reflexa, is, according to the author, composed entirely of cells, and is the nourishment destined for the embryo, being taken up after solution by the absorbent cells of the villi. By tracing the cavities of the vessels of the gravid uterus from without inwards, as had formerly been done by Professor Owen, the author verified the statements of certain anatomists, that the vessels pass from the uterus into the decidua, and open on the internal surface of the latter by oblique valvular orifices. He likewise observed, that the meshes enclosed by the uterine veins become smaller and more ribbon-shaped near the cavity of the placenta, and that in that cavity they represent the appearance of hollow threads, which pass in great numbers from the uterine surface of the organ on to the extremities and sides of the villi, and also from villus to villus. Along the cavities of these threads the cellular mass of the decidua becomes continuous with the external cells of the villi.

From these observations, Mr Goodsir concluded that the sac of the placenta is a network of enlarged decidual vessels, the meshes of which have been reduced to hollow threads; and, secondly, that not only is the external membrane of the villi a part of the mother, being a portion of the membrane of her vascular system, but that the external cells also are maternal, being decidual cells continuous, along the hollow threads, with the general mass of the decidua.

Mr Goodsir stated in conclusion

1. That the external membrane and the external cells of the villi constitute together the central division of the placental decidua, or the principal maternal portion of the organ, the cells being secreting cells destined to separate from the blood of the mother a matter proper for the nourishment of the foetus.

2. That the villi present, in addition, an internal membrane and internal cells, which together constituted, at an earlier period, the villi of the non vascular chorion; that the internal cells are absorb

ing cells, like the chyle cells of the intestinal tube, taking up for the fœtus the matter secreted by the external cells.

3. That the placenta not only performs the function of a lung, but also that of a gastro-intestinal mucous membrane.

2. On the Mode in which Sound is produced and diffused, and on the Vibrations caused in the quality of Sound by substance and form. By Sir George S. Mackenzie, Bart.

The following Donations of Books to the Society's Library were announced.

Voyage dans la Russie Méridionale et la Crimée, par M. Anatole de Demidoff. Tome 4, avec un Atlas des Planches.-By the

Author.

Bulletin de la Société Géologique de France, from 15th March to 9th September 1841.-By the Society.

Proceedings of the Glasgow Philosophical Society, 1841-42.-By the Society.

The following Gentlemen were duly elected Ordinary Fellows of the Society :-Joseph Mitchell, Esq., civil engineer; Duncan Davidson, Esq. of Tulloch.

Monday, 27th February 1843.

Dr ABERCROMBIE, Vice-President, in the Chair. The following communication was read.

Papers on Glaciers. No. 2, describing the Rate of Motion of the Ice of the Mer de Glace, deduced from observation. By Professor Forbes.

The author detailed in this paper the methods of observation by which he was enabled to ascertain the daily and even hourly motion of different parts of the glacier.

The following are some of the principal results :

I. In the particular case of the Mer de Glace, the motion of the higher parts of the glacier are on the whole slower than those of its lower portion, but the motion of the middle region is slower than either.

The following table, the result of observations at a series of ascend ing stations, will authorize this conclusion.