TRANSACTIONS OF THE SECTIONS. 75 



this view of the case, and Mr. Clark, who has endeavoured to disprove the existence 

 of separate branchial currents in all the bivalves, has more recently entered into 

 many details of experiments to show that no internal communication exists between 

 the two siphons of the genus Pholas. 



That the Pholades and MyadcB, as well as other bivalves, do draw in a current of 

 water by the branchial siphon, which is expelled by the anal one, the authors of this 

 paper have long known from actual observation, confirmed by recent investigations ; 

 but to answer the objections raised on anatomical grounds, they have found it ne- 

 cessary to examine the internal structure of these animals with greater care than 

 they had hitherto done. The result has been highly satisfactory, not only proving 

 the existence of an internal communication between the siphons, but opening out new 

 views of branchial action and its subserviency to the sustentation of the animal. The 

 communication is found to take place through minute apertures between the meshes 

 of the gills themselves. Each of the gill-plates or branchial leaflets consists of two 

 laminae united at the ventral margin, and likewise attached to each other in trans- 

 verse lines running across the gills throughout their whole extent, and forming in the 

 interspaces a series of parallel tubes which open into the anal or dorsal chamber, and 

 are thus in communication with the excurrent siphon. The minute reticulated blood- 

 vessels of the branchial laminas, forming the walls of these tubes, are found when ex- 

 amined by a high power of the microscope to be open between the meshes, which are 

 minutely ciliated, allowing the passage of the water into the tubes and from thence 

 into the anal chamber. The gill-laminae thus act like a sieve, not only aerating the 

 branchial vessels most completely, but also straining the water, by which means the 

 nutritive particles suspended in it are left on the outer surface of the gill, and by 

 means of vibratory cilia are conveyed to the ventral margin, and thence along a mar- 

 ginal groove to the mouth. By laying open a living Pholas and colouring the water 

 with indigo, the whole of this apparatus may be seen in action, which certainly forms 

 one of the most beautifully adapted organic mechanisms that can be looked upon. As 

 a breathing organ it is very complete ; as a prehensile organ for receiving food, it is 

 unrivalled for the minuteness and beauty of its structure. 



An examination of the branchiae oi Mya, PuUastra, Cardium, Osirea, and Mytilus, 

 shows them to be formed after the same plan, and induces the authors to beUeve that 

 the sieve-like character of the branchice and the mode of action here described pre- 

 dominate throughout the whole order of the LameUibranchiata as well as in that of 

 Tunicata, whose branchiae are known to have a similar structure. 



On Sea Sickness, and a New Remedy for its Prevention. By J. Atkinson. 



The writer alluded to the method of curing sea-sickness proposed by M. F. Curie 

 in the ' Comptes Rendus' of the French Academy of Sciences, September 30th, 1850, 

 which consists of drawing in the breath as the vessel descends and exhaling as it 

 ascends on the billows, — being based on the supposition that the complaint arises 

 from the upward and downward movements of the diaphragm acting on the phrenetic 

 nerves in an unusual manner. After remarking on various motions, as those pro- 

 duced by swinging and by riding in a carriage, by which nausea is often induced, 

 and showing that voluntary operations performed by mechanics and labourers in- 

 volving the same kind of movements of the diaphragm, &c. do not cause similar 

 unpleasant results, he proceeded to detail the method which he had found successful 

 in preventing sea-sickness, as follows : — 



" Let a person on ship-board, when the vessel is bounding over the waves, seat 

 himself, and take hold of a tumbler nearly filled with water or other liquid, and at 

 the same time make an eflPort to prevent the liquid from running over, by keeping 

 the mouth of the glass horizontal, or nearly so. When doing this, from the motion 

 of the vessel, his hand and arm will seem to be drawn into different positions, as if 

 the glass were attracted by a powerful magnet. Continuing his efforts to keep the 

 mouth of the glass horizontal, let him allow his hand, arm and body to go through 

 the various movements, — as those observed in sawing, planing, pumping, throwing 

 a quoit, &c. — which they will be impelled, without fatigue, almost irresistibly to 

 perform, and he will find that this has the effect of preventing the giddiness and nausea 

 that the rolling and tossing of the vessel have a tendency to produce in inexperienced 



