24 



LIVING AND LIFELESS MATTER 



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 automatic- 

 ally. 



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 



n 



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

 cle, p, Protoplasm; n, nucleus. (From Sedgwick and Wilson.) 



protoplasm of an Amoeba or of Nitella, the cilia of an epithelium, 

 move faster with a slight increase in temperature. Reduction 

 of temperature on the other hand, retards these movements, 

 until with increasing cold there comes a temperature in which 

 all activity ceases. Most organisms are destroyed at the tem- 

 perature 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 



