..^-EPIDERMIS 



— CUTIS CDERMIS) 



•CONNECTIVE TISSUE 



tzzzzzzz zzzzzz+-~ MUSCLt 



k^\^\\\\\^ -BONE 



'2ZZZZZZZZZZZZ2. 



' . TT~ FRESHLY CUT SURFACE 



REGION OF DEDIFFERENTIATE 



V//////////< — °°o % 1 1< 



vzzzzzzzzzl*-*\Y° 



COMPLETED REGENERATION 



Fig. 160. Schematic representation of the cellular changes after cutting the 

 limb of a larval salamander. Top: A clean cut traverses epidermis, dermis, con- 

 nective tissue, muscle, and bone (nerves and blood vessels not shown). Next 

 lower: A blastema forms. The exact origin is not known. We have represented 

 the blastema as forming from the dedifferentiated cells of the various tissues of 

 the limb plus cells which migrate in from the epidermis. Third figure: What- 

 ever the exact origin of the blastema, the process of dedifferentiation is soon 

 checked and then cells of the blastema begin to re- differentiate into muscle, bone, 

 etc. Bottom: Regeneration completed. The blastema has differentiated into the 

 missing part. 



237 



