THE INSURGENCE OF LIFE 153 



Some interesting illustrations of tenacity of life have been 

 afforded by recent experiments on the surviving-power of 

 tissues cut off from the living body. In suitable culture- 

 media they can be kept alive for many days and may even 

 grow. At a variable point, differing for different tissues 

 and media, growth becomes slow and stops and the living 

 fragment dies. In this connexion Alexis Carrel has de- 

 monstrated a very instructive fact, showing that the 

 death may be due to an accumulation of waste products 

 and is not inevitable. If the dying fragment is lifted on a 

 cataract-knife and bathed and fed, and bathed and fed 

 again, it may get a new lease of hfe. It rejuvenesces. 

 After nine washings a fragment of connective tissue grew 

 with great activity on the thirty-fourth day after its 

 excision from the organism. Thus, within Iknits, senescence 

 and death are contingent, not necessary phenomena. 



The automatism of part of a body is often gruesome. A 

 turtle's heart will live for many days after its quondam 

 possessor has been made into soup. A fractional part of a 

 silk moth was observed by Professor V. L. Kellogg to ' Uve ' 

 for more than a day, responding to stimulus, and actually 

 extruding the ovipositor and laying a few eggs. The 

 separated anterior half of a wasp will go on sucking 

 sjTTup, and the posterior halt will sting. We are impressed 

 on the one hand by the delicacy, on the other hand by 

 the toughness of life. 



The 'Big Trees '.—In the 'Big Tree' (Sequoia 

 gigantea) of the western slopes of the Sierra Nevada 

 range and in the ' Redwood ' (Sequoia sempervirens) 

 of the Coast Ranges, we have the impressive surviving 

 representatives of an ancient genus (dating from the 

 Cretaceous) that once spread over the Northern 



