EFFECTS OF HEDUCTION OF HEAT. 



10? 



animal functions. Eossbach proved that the rhythmical con- 

 tractions of the contractile vesicle in Infusoria are very' remark- 

 ably aifected 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- 



Fio. 28.— Tlie Infusoria observed by Bossbach, a, CJdlodon cuaillulua; i, Eupkles 

 Charon ; c, Stylonychia puslulata. 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 Ghilodon cucuUulua contracts 

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

 times, while at 1 5° 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 the sea-level. 



