264 HYBERNATION. 



of total torpidity ; for the only indication of irritability 

 perceptible during this period is a slight contraction of the 

 collar of the mantle when touched on removing the epi- 

 phragm. He found that there was no digestion ; the heart 

 at first beat feebly, and with a very slow pulsation ; but at 

 a later period it was found to have stopped, and the cir- 

 culation was entirely suspended ; respiration ceased ; no ani- 

 mal heat, which even in the summer, when respiration and 

 circulation are most lively, does not exceed one degree above 

 the surrounding atmosphere, was evolved ; no secretions nor 

 wasting function went on, neither any growth or reproduc- 

 tion of new parts. " In our climate it is about the begin- 

 ning of April, soon after the song of the cuckoo begins and 

 the swallows appear, that the snails leave their torpid state ; 

 varying a little, however, according to the season. The 

 mode by which their escape from confinement is effected 

 is simple and easily comprehended. The air which is con- 

 tained in the different cells, and which had been expired on 

 the animal withdrawing itself farther and farther into the 

 shell after the formation of the operculum, is again inspired, 

 and each separate membranous partition broken by the pres- 

 sure of the hinder part of the foot projected through the 

 mantle. When it arrives at the calcareous operculum, the 

 animal, making a last effort, bursts and detaches its most 

 obtuse angle. Then insinuating by little and little the edge 

 of the foot between the shell and the operculum it forces 

 the latter off, or breaks it away. The animal then comes 

 forth, walks, and immediately begins feeding, with an ap- 

 petite excited, doubtless, by an abstinence of six or seven 

 months." * 



Such is M. Gaspard's account of the reviviscency of Helix 

 pomatia, and the process must be still simpler in the other 

 species ; for they have merely to rupture a single horny or 

 semiarelatinous membrane. But there has been a difference 

 of opinion relative to the source of the air which is first 

 respired. Gaspard, you will observe, says that that portion 

 which is confined between the layers of the epiphragm is the 

 first inhaled; and, in coincidence with this opinion, we must 

 infer that the species with a single membrane respire in the 

 first instance the air behind it, and then, by their own 

 efforts, burst their prison wall. A very different explana- 

 tion of the process has been advanced by Sir Everard Home. 

 He says: "When warmth and moisture are applied, the 

 membranous film (of the garden snail) falls off; a globule of 



* Zool. Journ. i. 99. 



