102 MANUAL OF ELEMENT ARY ZOOLOGY 



the condition of the other cells of the body is in contrast. 

 Each of them consists of a portion of the protoplasm of 

 the organism in which certain of its powers are highly 

 developed, while others are degraded or lost. It is 

 probable that all protoplasm retains irritability, either to 

 stimuli through a nerve or at least to changes in the 



w.f. 



Fig. 6i. — Areolar connective tissue of the frog. 



c, Cells ; €./., elastic fibres ; w./., white fibres. 



composition of the fluid that surrounds it. It may be, 

 too, that automatism of a kind is widespread ; and dis- 

 integration and assimilation are of course universal. But 

 in most tissues the cells have lost in the adult the power 

 of reproduction, and certain of the modes of appearance 

 of the energy liberated by disintegration are developed 

 at the expense of others. Thus in a nerve cell con- 

 duction is highly developed and contraction lost, while 



