394 GENERAL PHYSIOLOGY 



increase with increasing temperature. The same phenomena can 

 be observed as easily and perhaps more clearly in Infusoria 

 with the warm stage. Rossbach, who first made such investigations 

 upon various Oiliata, describes how the ciliary motion suddenly in- 

 creases in rate, so that at 25 C. the Infusoria begin " to shoot 

 here and there like arrows," and at 30 35 C. their motions 

 become really furious. 



Muscle behaves analogously. If a frog's muscle be hung in a 

 0'5 per cent, solution of common salt, the temperature of which 



FIG. 182. Oral mucous membrane of the frog stretched upon a cork frame. 



is rapidly increased, the muscle shortens gradually with 

 increasing temperature from about 28 C. on, until at about 

 45 C. its contraction has reached its maximum. But if the 

 muscle be dipped suddenly into a salt solution of 45 C., 

 there appears at once a sudden contraction. The irritability of 

 muscle is also increased with rising temperature. 



Thus, everywhere in living nature, the law is met 'with, that within 

 certain limits increasing temperature acts to augment vital processes. 



I. The Phenomena of Depression 



Falling temperature produces effects opposite to those of rising 

 temperature. If the temperature be constantly lowered from the 

 average at which an organism normally exists, it is found that the 

 vital phenomena constantly decrease in energy, and that from a 

 certain low degree on which point is very different for different 

 organisms and different phenomena they are no longer percep- 

 tible. Thus, at temperatures below 10 C. yeast no longer decom- 

 poses grape-sugar ; at 2 3 C. the development of sea-urchin eggs 

 undergoing division is at a standstill ; at a little above C. Amoeba 

 ceases its motions, and when cooled rapidly is fixed in the form 

 which it possessed (Fig. 183, C). At a certain lower degree 

 protoplasm takes on cold-rigour. Warming above this point is 

 sufficient to dissipate the rigour and allow the phenomena to 

 appear again. But, if the temperature is reduced below this point, 

 a point is finally reached at which the vital capacity is abolished } 



