THE LAWS OF LIVING PROTOPLASM 1 9 



trated by taking the heart of a frog from the 

 recently chloroformed animal and placing it in salt 

 water. The heart now begins to beat in a rhythmic 

 fashion. Living cells can be taken from various 

 animals and when placed in an artificial culture 

 can be kept alive for months at a time. In one 

 instance connective-tissue cells, isolated from the 

 heart of a chick embryo, have been kept alive for 

 seven years. Under such conditions they are en- 

 tirely separated from the living animal; and, while 

 able to grow under this abnormal condition, they 

 cannot give rise to a new individual like the animal 

 from which they were taken. The influence that 

 life thus has on the material substance which 

 composes the body of living things is important. 

 When changes occur in non-living material disin- 

 tegration and simplification usually follow; while 

 the living organisms possess something that is 

 absent from the non-living. A general term is 

 used to express what appears to happen, although 

 it does not clearly define the process. This term 

 is adaptation. When some disturbance acts upon 

 the structure or internal vital conditions, the living 

 body adapts itself. There is a readjustment, so 

 that the wound heals or the poisons from a given 

 disease are overcome. After one of these read- 

 justments, we have the same recognizable organ- 

 ism. The living body can maintain itself under 

 a wide range of external conditions and undergo 



