METHODS OF PHYSIOLOGICAL ANALYSIS 59 



become the same as that of the region of the intact body which the piece 

 represents, or does it remain above or fall below that? Sixth, does loss of 

 body fluids or blood in consequence of section affect the respiratory rate 

 of pieces? Seventh, in pieces which undergo reconstitution is respiratory 

 rate altered by the reconstitutional activities, and, if so, how soon after 

 section does this alteration occur? Eighth, if pieces are motile, is motor 

 activity of pieces from different body-levels different in degree, and, if it 

 is, to what extent does this affect respiration? In certain cases the ques- 

 tion of occurrence or of intensity of anaerobic respiration must also be 

 considered. 



At present it is not possible to answer all these questions with certainty. 

 For example, we cannot be entirely certain whether the respiratory rate 

 of an isolated piece from a certain body-level is the same as when the piece 

 was a part of the intact body; nor can we determine with certainty when 

 reconstitutional activity begins to affect the respiratory rate, although it 

 appears beyond question that it does increase the rate. As a matter of 

 fact, in most animal species thus far investigated the respiratory rate is un- 

 doubtedly increased, sometimes very greatly, immediately following sec- 

 tion and gradually decreases during one to several hours following; the 

 rate of all the pieces together may finally become about the same as that 

 of the animal before section, but we have no means of knowing that the 

 rate of each piece is the same as when it was part of the intact body. The 

 total rate of pieces of some other animals may fall below that of the intact 

 animal; consequently, the significance of differences in pieces from differ- 

 ent levels becomes still more uncertain. Motor activity presents another 

 difficulty in motile animals. In planarians, for example, pieces above a 

 certain fraction of body length from anterior regions of the body show, in 

 general, more motor activity for some time after section than pieces from 

 more posterior levels. These differences, however, can be practically elimi- 

 nated by decreasing length of pieces, controlling illumination, and provid- 

 ing conditions favorable to aggregation of the pieces. In naked-bodied 

 aquatic forms which can withstand only brief exposure to air, weighing of 

 pieces presents certain difficulties. Some forms secrete considerable slime 

 when exposed to air, and transfer connected with weighing may also in- 

 crease slime production. If perisarc or other skeletal substances are pres- 

 ent, they usually differ in amount at different body-levels and become a 

 factor in weight. 



Elongated organisms of considerable size, at least several millimeters 

 in length, and without great regional differences are the most favorable 



