Intelligence and Miscellaneous Articles. 403 



gress of the postglacial denudation. Thi3 denudation had its in- 

 ception in the upheaval of a portion of the glacial sea-bed, and was 

 accompanied by a long succession of subterraneous disturbances, 

 which have brought up the Secondary and Tertiary rocks of the south 

 and west to the elevations they now occupy, and left the early 

 emerged portion of this sea-bed (represented by the detached tracts 

 of the Upper and Middle Glacial formations) at lower levels than 

 much of the denuded area of the south and west. 



LIII. Intelligence and Miscellaneous Articles. 



INVESTIGATIONS ON THE INFLUENCE OF HEAT ON THE MECHA- 

 NICAL FORCE OF FROGS' MUSCLE. BY M. CHMOULEVITCH. 



"I N investigating the influence of temperature on muscles at rest, I 

 -*- was led to assume that all their physical properties experience 

 great changes, even within very narrow limits of temperature. It was 

 natural to assume a priori that these differences must also deter- 

 mine changes in their physiological functions. For this reason I 

 decided to investigate the action of heat on the mechanical force of 

 the muscle. 



In making the experiment, the gastrocnemian muscle of the frog 

 was fixed by its tendon in a vessel containing a solution of chloride 

 of sodium (0'65 per cent.) at a given temperature. The upper inser- 

 tion of the muscle was fixed to the short arm of a lever moving 

 about a horizontal axis, the long arm of which marked upon a rota- 

 ting cylinder the heights to which the weight applied to the same 

 arm was raised. I obtained the following results : — 



(1) The mechanical force of the muscle increases up to from 30° 

 to 33° according to its length and tension. 



(2) The increase in the height to which the weight is raised du- 

 ring the increase of temperature is greater the less the weight. 



(3) In the case of each muscle there is a certain tension under 

 which it retains the same length at different temperatures. 



(4) When the temperature is raised to more than from 30° to 33° 

 its mechanical work is seen to diminish rapidly ; and a point is soon 

 reached at which, while supporting a given weight, it no longer con- 

 tracts ; its work is then equal to zero ; I designate it by the name 

 zero work. 



(5) Zero work is reached the sooner the greater the weight which 

 the muscle supports. This proves that the muscle losing its property 

 of contracting at certain temperatures is not due to a chemical action 

 of temperature on the substance of the muscle, in which case the 

 required temperature would be constant and would not change 

 with the weight ; it rather arises from a change in the purely physical 

 relations of the molecules of the muscles produced by the high 

 temperature. We have in support of this opinion the fact that 



(6) The muscle need only be lowered in temperature to restore to 



