384 Royal Society. 



times of two. In the situation of a valve and centrad of the inser- 

 tion of its flaps, the veins present the usual dilatations or sinuses. 

 The valves are a reduplication of the clear innermost coat of the 

 vein, with sometimes an intervening layer of cellular tissue. 



The veins closely accompany the arteries, the nerve only inter- 

 vening'. 



The contractility of the arteries the author finds altogether differ- 

 ent from that of the veins, heing tonic, not rythmical. He has not 

 heen able to observe unequivocal evidences of tonic contractility of 

 the veins, which they have been alleged to possess. 



In figure 3, of drawing No. 1, illustrating his paper, the author 

 represents, in reference to this point, an artery and a vein, as ob- 

 served immediately after pressure had been applied over them. The 

 artery is seen constricted at intervals both above and below the place 

 of pressure. The vein is not so constricted, but at the place where 

 the pressure was applied there is seen a greyish granular deposit 

 of lymph within the vessel, giving rise to an appearance of constric- 

 tion by narrowing the stream of blood. On watching a vein in this 

 state, the author has observed portions of the lymphy deposit car- 

 ried away by the stream of blood, with corresponding enlargement 

 of the channel. 



The author further finds that nowhere do the arteries and veins 

 of the web of the bat's wing directly communicate, as has also been 

 alleged ; the only communication being the usual one through the 

 medium of capillaries. 



In an appendix to this paper, the author describes the result of 

 his microscopical examination of the structure of the veins and arte- 

 ries. Both artery and vein have a middle coat of circularly disposed 

 muscular fibres ; but the appearance of the fibres is different in the 

 two vessels. The fibres of the vein are s g* 00 dth m - Droa d. pale, 

 greyish, semitransparent and granular looking. In general aspect, 

 they very much resemble the muscular fibres of the lymphatic hearts 

 of the frog; but in none did the author detect an unequivocal ap- 

 pearance of transverse marking. The fibres of the middle coat of 

 the artery are not so pale looking, are clearer, and exhibit a more 

 strongly marked contour. 



2. " Some Observations on the Ova of the Salmonidse." By John 

 Davy, M.D., F.R.S. Lond. and Ed., Inspector-General of Army 

 Hospitals, &c. 



The author prefaces his observations by a quotation from the 

 work of M. Vogt on the Embryology of the Salmonida?, in which 

 a remarkable property of the vitellus is described, viz. its coagula- 

 tion by admixture with water. 



This inquirer's experiments were made chiefly on the ova of the 

 Palce (Coregonus Palma, Cuv.); the author's mostly on the ova of 

 the Charr (Salmo Umbla). After giving a description of the mature 

 eggs of this fish, he details the trials instituted by him : — 1st, on the 

 action of water, showing its coagulating effect, except when added 

 in very minute quantity. 2ndly, on the action of heat ; how that a 

 dry heat, even so high as that of 212° Fahr., occasions the contrac- 



