EFFECTS OF REDUCTION OF HEAT. 



107 



animal functions. Rossbach proved that the rhythmical con- 

 tractions of the contractile vesicle in Infusoria are very remark- 

 ably affected by a low temperature. He found by very carefully 

 conducted experiments (fig. 27) that the pulsations of these vesicles 

 were generally carried on most regularly and rapidly in a tempe- 

 rature varying between 15 and 25 centigrade. But the lower- 



FIG. 28. The Infusoria observed by Rossbach. a, Chilodon ctietllttliu ; i, Eupktes 

 Cftan/n ; e, Sit/Ion fdiia puitulaia. Highly magnified. 



ing of the temperature to 5 above freezing point (5 3 centigrade) 

 has a quite different effect on the different species : thus, at this 

 low temperature the vesicle of Chilodon cucullulus contracts 

 seven times in a minute, that of Stylonychia pustulata only three 

 times, while at 15 there are fifteen pulsations per minute in 

 each. At IG above zero * the length of one pulsation in, 



* Zero, in the centigrade thermometer, is freezing point ; 100 the 

 boiling point of water at the sea-level. 



