502 British Association for the Advancement of Science. 



On the Formation of a Natural Arrangement of Plants for a Botanic 

 Garden. By Mr. Niven.' 



The principal object of this plan is to divide the exotic from the 

 European plants by a serpentine walk, bringing the allied species in 

 juxtaposition by the numerous curvatures. 



On Ph&nogamous Plants and Ferns indigenous to Ireland which 

 are not found in England or Scotland. By Mr. Mackay. 



Mr. Mackay having been requested to present a general report on 

 this and other branches of the botany of Ireland at the next meeting 

 of the Association, this communication is omitted, as well as other 

 notices of the same nature by Mr. Babington, Mr. Curtis, and Pro- 

 fessor Graham. 



Various other notices connected with the subjects of the papers 

 were received from Dr. Coulter, Professor Graham, Mr. Curtis, 

 Colonel Sykes, Mr. Fox, Mr. Waterhouse, Mr. J. B. Yates, Dr. 

 Traill, Mr. Haliday, and Mr. Marshall. 



MEDICAL SCIENCE. 



On the Peculiarities of the Circidating Organs in Diving Animals. 

 By John Houston, M.D., M.R.I.A., fyc. $c. 



The circulation of the fluids in living animals, though mainly car- 

 ried on by the influence of the vital powers, is nevertheless to a cer- 

 tain extent amenable to the general laws of hydraulics. Gravity, 

 motion of the particles of the solids upon each other, the respiratory 

 function, pressure on the surface of the body, all, under various 

 modifications, promote or retard the movement of the fluids along 

 their vessels. But of all the collateral circumstances exerting an 

 influence of this nature, the action of the chest and lungs appears, in 

 warm-blooded animals, to be one of the most important. Suspen- 

 sion of respiration puts a stop to the circulation of the blood through 

 the lungs ; this fluid under such circumstances stagnates in the ves- 

 sels leading to these organs, and cannot pass forwards until air be 

 freely readmitted : death in a few moments is the inevitable conse- 

 quence of such interruption. Animals living in atmospheric air 

 cannot exist under a state of suspended respiration so long as those 

 whose natural habitation is the water. The most expert diver has 

 never been known to remain submersed for more than two minutes 

 at a time, whilst it is well known that the whale can remain under 

 water for upwards of twenty. Now, the arrangement of the respira- 

 tory and circulating organs in man and cetaceous animals, and the 

 influence of these two systems on each other, being the same, though 

 their powers of suspending respiration with impunity are very dis- 

 similar, we naturally inquire, on what does this latter difference 

 depend ? 



Independently of the suspension to respiration which occurs in 



