EFFECTS OF EEDUCTION OF HEAT. 



m 



animal functions. Eossbach 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- 



FlG. 28.- 



-Tlie Infusoria observed by Eossbach. 

 Chavon ; c, Stylanychia pustulata. 



I, Chilodon CMcnllulus; h, Evplcles 

 Highly magnified. 



ing of the temperature to 5° above freezing point (5° 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 Stylanychia pustulata only three 

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

 each. At 10° above zero * the length of one pulsation in 



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

 boiling point of water at tiie sea-level. 



