24 



LIVING AND LIFELESS MATTER 



tary muscles, are used mainly for locomotion, food getting and 

 other ordinary purposes in the life of the individual. Others, 

 the involuntary muscles, like those of digestive tract and heart, 

 work automatically. 



All three of these manifestations of vitality are closely con- 

 nected. Form and appearance of protoplasm are largely de- 

 pendent upon movement of the protoplasmic mass, whole or in 

 part. Movement of any type, in turn is dependent upon the 

 conditions of the surrounding medium, or the environment. 

 It is a general truth that heat accelerates and cold diminishes, 

 all within certain limits, the activities of protoplasm. The 

 protoplasm of an Amoeba or of Nitella, the cilia of an epithe- 

 lium, move faster with a slight increase in temperature. Reduc- 



i 



i,'iirnriin 



l'liT/.<;t 



fig 

 . 



. 



FIG. ii. Finer structure of a muscle cell (on left) and change of form of a 

 muscle. A, at rest; B, contracted, p, Protoplasm; w, nucleus. (From Sedgwick 

 and Wilson.) 



tion of temperature, on the other hand, retards these move- 

 ments, until with increasing cold there comes a temperature in 

 which all activity ceases. Most organisms are destroyed at the 

 temperature of boiling water, although by special adaptations 

 some are able to withstand a much higher temperature (bacteria 

 spores). High temperatures cause the coagulation of certain 

 substances in protoplasm, and lead to what is called heat rigor 

 (rigor caloris), usually between 40 and 50 C. There is no 



