i54 Royal Societj/. 



fixed by a wire frame in the upper part of the jar. The animal, at 

 the end of the experiment, is withdrawn under mercury, without 

 displacing the jar ; the space it had occupied is filled with an equal 

 volume of atmospheric air admitted into the jar; and the volume of 

 oxygen gas absorbed is estimated by the column of water which 

 has risen in the gauge. 



From the facts detailed by Harvey, Goodwyn and others, which 

 establish that in asphyxia the left ventricle of the heart ceases to 

 contract before the right ventricle, the author infers that the irrita- 

 bility of the latter is greater than that of the former; and proposes 

 to distinguish the first as urterio-contractile, and the latter as veno- 

 contractile, from the circumstance of their being stimulated respec- 

 tively by arterial and by venous blood. He considers the power of 

 bearing suspended respiration as ameasure of irritability, which may 

 be expressed by the length of time during which an animal can sup- 

 port the suspension of this function. He then shows that, conform- 

 ably to these definitions, the foetus before birth, the reptile, and the 

 molluscous animal possess a much higher degree of irritability than 

 the adult, or than animals belonging to the class of mammalia and 

 birds ; in which the quantity of respiration being very great, the 

 irritability is proportionally small. 



He then proceeds to consider the phaenomena of hybernation; 

 and shows that they are very similar to those of the ordinary sleep 

 of the same animals, but differ from those of the sleep of animals 

 which do not hybernate. In the former case the respiration is 

 nearly, if not wholly, suspended, and the temperature greatly re- 

 duced ; but the circulation continues unimpaired. He notices dif- 

 ferences also in the habits of different hybernating animals, some of 

 which frequently awake from their slumber during the winter, while 

 with others the lethargy is uninterrupted. The state of hybernation 

 should, he thinks, be carefully distinguished from ihe torpor induced 

 by excessive cold ; the former being a conservative, the latter a 

 destructive process. The exclusion of atmospheric air, which is 

 speedily fatal to the animal in its active state, is sustained with per- 

 fect impunity during hybernation, the respiration being then entirely 

 suspended. The animal being at such times reduced to a state 

 analogous to that of the reptile, but in a still higher degree, the 

 irritability is much increased: the heart continues to beat without 

 the stimulus of aerated blood, and the circulation is kept up with 

 perfect regularity. This latter fact was ascertained by actual ob- 

 servation in the case of the bat, by adjusting the wing of the animal, 

 so as to admit of its being placed in the field of a microscope with- 

 out disturbing its repose. The experiments of Mangili are quoted 

 in proof of the longer continuance of the action of the heart after 

 decapitation, if the experiment be made in the hybernating state, 

 than if it be made when the animal is in its ordinary state of acti- 

 vity. 



Animals, during hybernation, are easily roused from their le- 

 thargy, and restored to sensibility and activity; and the muscles do 

 not appear to be affected with the slightest rigidity : the respiration 



