animal heat ; and arrives at the following results. He finds that the blood is capable of absorbing oxygen both from atmospheric air, and from oxygen gas, independently of putrefaction. After blood has been agitated in common air, a trace of carbonic acid, not ex- ceeding one per cent., is found in the residual air; but when pure oxygen is employed, no carbonic acid can be detected in it by the most carefully conducted trials. When pure carbonic acid is brought into contact with blood, or serum, over mercury, and moderately agitated, the absorption of gas exceeds the volume of the fluid. Both arterial and venous blood are rendered very dark, and serum more liquid by the absorption of this gas to saturation. Serum, in its healthy state, is incapable of absorbing oxygen, or of immediate- ly furnishing carbon to form carbonic acid : and after it has ab- sorbed carbonic acid, only one-tenth of the absorbed gas is expelled by successive agitation with atmospheric air, or with hydrogen. The author is inchned to think that the alkali in the blood, in its healthiest condition, is in the state of a sesquicarbonate. In the majority of trials manifest indications of the disengagement of air from blood in vacuo were obtained : but as it occasionally happened that no air could be thus extricated, the author is induced to believe that the quantity of air contained in the blood is variable : and he has found this air to consist solely of carbonic acid gas. It would also appear, from the experiments detailed in this paper, that a por- tion of oxygen exists in the blood, not capable of being extracted by the air-pump, yet capable of entering into combination with ni- trous gas ; and existing in largest proportion in arterial blood. The absorption of oxygen by blood is attended with an increase of tem- perature.
The experiments of the author tend to show that the lungs are absorbing and secreting, and perhaps also inhahng organs, and that their pecuhar function is to introduce oxygen into the blood and separate carbonic acid from the blood : and they favour the idea that animal heat is owing, first, to the fixation or condensation of oxygen in the blood in the lungs during its conversion from venous to arte- rial ; and secondly, to the combinations into which it enters in the circulation in connexion with the different secretions and changes essential to animal life.
" On the Geometrical Forms of Turbinated and Discoid Shells." By the Rev. H. Moseley, Professor of Natural Philosophy and As- tronomy in King's College, London. Communicated by Thomas Bell, Esq., F.R.S.
This paper is occupied by an investigation of certain mathemati- cal principles which the author considers as governing the formation of turbinated and discoid shells. According to these views, all such shells may be conceived to be generated by the revolution about a fixed axis of the perimeter of a geometrical figure, which, remaining always similar to itself, increases continually its dimensions. The spiral lines which are observable on the opercula of certain classes of shells, taken in connexion with the well-known properties of the
