42 



FUNDAMENTAL STRUCTURE OF PROTOPLASM 



described, the coagulation may spread successively in the protoplasm 

 as a chain reaction, a contraction of the proteins at a site of proto- 

 plasm becoming in turn a stimulus on the other proteins or on the ele- 

 mentary bodies surrounding them (Fig. 6). Such coagulation or con- 

 traction of the elementary bodies is, as a rule, reversible, and when 

 agents having caused the change, /. e., stimuli, are removed, they can 

 resume their former state. 



Stimulus Stimulus 



J 1 



zziz: =: 1 F!™'""^ + «'N -^ coo- + h^n — coo- + h,n — coo- 



bodies 



-OOC NH, + -OOC NH3+ -OOC NH3 + 



+ HsN coo- + H3N coo- + H3N coo- 





+ H3N coo- ^'■^^o + H3N — coo- 



-OOC NH3 -h -OOC NH3 + -OOC NH, -t- 



+ H3N — COO- -I- H3N — COO- + H3N — coo- 



1WP 



#'% 







-OOC KH3+ O"' '"-t. -OOC NH, + 



+ H3N COO- + H3N coo- + H3N COO- 





WF 





TTfP 



TWO 



'BIT? 



omrp 



Fig. 6. Transmissible coagulation of protoplasm. In the left, the manner 

 in which elementary bodies are coagulated into minute bodies, and in 

 the right, the manner in which polar groups of protein molecules 

 undergo mutual association are illustrated. 



This may be the principal feature of the irritability of protoplasm. 

 The contraction of elementary bodies joined with one another along 

 the long axis may account for the various functions of protoplasm, 

 such as changes in cell shape, the activity and direction of cytoplasmic 



