360 
DR. MARSHALL HALL ON HYBERNATION. 
different condition of the system, — that of torpor. Sleep is the medium be- 
tween such moderate cold and the phenomena of hybernation ; torpor is the 
immediate effect of the severer degrees of cold. 
This investigation naturally leads to that of the comparative conditions of 
the respiration and of the irritability, in the pupa and perfect states of some 
species of the insect tribes. There is much reason to suppose that these states 
are respectively similar to those of lethargy and activity in the hybernating 
animal. 
