14(5 LIBBIE H. HYMAN 



The rate of metabolism of pieces is not the same as that of cor- 

 responding parts of the intact worm because, as Child has shown 

 ('14 d), the rate of metabolism is increased by the operation of 

 cutting; this increase is greater the shorter the piece, and the 

 lower its previous rate as part of the axial gradient. These 

 facts have been demonstrated not only by the increased sus- 

 ceptibility of the pieces to cyanide, but also by their increased 

 CO2 production in Tashiro's biometer. Similarly, in all the 

 oligochaetes which I have tested Dero, Lumbriculus, Tubifex, 

 and Limnodrilus — stimulation results from section. In long pieces 

 there is little stimulation, and the disintegration gradient of the 

 intact worm is preserved in the pieces, except for increased 

 susceptibility at the cut surfaces. Short pieces are stimulated 

 to a much greater extent, and their disintegration in cyanide 

 takes place without regard to the previous gradient; it begins at 

 the cut surfaces and proceeds towards the middle. It is there- 

 fore the region of the wound which is the seat of the stimulation, 

 and in short pieces the wound regions practically include all of 

 the piece. Stimulation as a result of injury is undoubtedly a 

 general phenomenon exhibited by living matter (Tashiro, '13), 

 and gives us a simple explanation of such facts as the current of 

 injury of nerve and muscle. 



The degree of stimulation of pieces is a function of their previous 

 axial posit'on, and this is particularly noticeable in short pieces. 

 The isolated head shows no stimulation; pieces from anterior 

 regions where the metabolic rate is high are stimulated to some 

 extent; pieces from middle regions where the rate is owest are 

 stimulated most ; pieces from the posterior region of high rate are 

 stimulated to a considerable extent, and ^:'nce they already 

 possessed a high rate before section, their rate after section is 

 usually higher than that of the middle pieces, although the rate 

 of the latter has been increased more relative to their previous 

 rate. The metabolic condition of the axial series of pieces is not, 

 therefore, the reverse of the metabolic gradient of the intact 

 animal, as is the case in Planaria, because of the existence in 

 oligochaetes of the posterior region of high rate. That this 

 posterior region is stimulated by section indicates, as I have al- 



