486 THE WONDER OF LIFE 



without regenerative power or only a little of it, we may 

 recall the familiar case of the turtle's heart, which, in 

 appropriate conditions, will continue beating for several 

 days after the bulk of the animal has been made into soup, 

 and has passed into a new incarnation. There it goes on 

 beating in its warm and humid glass case a fine illustra- 

 tion of local life. 



Of recent years very remarkable experiments have been 

 made in keeping pieces of tissue alive in suitable media 

 outside the body. What happens in most cases is that they 

 live on for a time, grow a little, and die. Perhaps we should 

 know a good deal if we understood why they die. It has 

 been suggested that the death may be contingent rather 

 than necessary, that it may be due, for instance, to the 

 accumulation of waste products. With this idea in mind, 

 Alexis Carrel has devised a system of artificial rejuven- 

 escence, washing the piece of tissue from time to time in 

 ' Ringer's solution ', and placing it in a medium of plasma 

 and distilled water. A piece of connective tissue revived 

 nine times after this bathing treatment staving off senes- 

 cence and death for more than a month after its removal 

 from the body. 



Every one knows that egg-cells can remain for a long 

 time alive but without developing. Much more remarkable 

 is the fact that spermatozoa can be kept alive in a salt 

 solution for a week. Very much more remarkable is the 

 fact that isolated red blood corpuscles, of the newt for 

 instance, can be kept alive for a fortnight. Jolly took a 

 small quantity of blood directly from the newt's heart, 

 put it in a tube placed in ice, and found the white blood 

 corpuscles alive after 4| months. Verily the tenacity of 

 life is great. 



