414 CM, CHILD 



cal condition and always from the same stock, are cut into fourths, 

 sixths, eighths, or twelfths; each lot of ten pieces representing 

 approximately the same region of the body is kept together and 

 isolated from other lots and its susceptibility tested at the desired 

 time after section. 



In all the susceptibility determinations of pieces presented 

 below animals from the same stock were used and great care was 

 exercised in selecting those of equal size, as experience has shown 

 that in a particular stock size is the best criterion of physiological 

 condition, and also in cutting the pieces so that they should rep- 

 resent as nearly as possible the same regions of the bodies of 

 different individuals. It is of course impossible to avoid some 

 differences in size and level of pieces but the results will show how 

 unimportant these differences are. In all susceptibility deter- 

 minations KCN 0.001 m was used in filtered water from the same 

 source and at the same temperature and the same quantity of 

 KCN solution was used in each case. 



In this manner the susceptibility of series of ten each of fourths, 

 sixths, and eights, of wellfed animals 18 mm. in length has been 

 determined, immediately, twelve, twenty-four, forty-eight, seventy- 

 two, ninety-six and one hundred and twenty hours after section, 

 and for some series of pieces three and six hours after section also. 

 For twelfths the susceptibility has been determined, immediately, 

 twenty-four and forty-eight hours after section, but it is impossible 

 to avoid considerable relative differences in size in pieces as small 

 as these and such differences complicate the results. With pieces 

 smaller than twelfths no general susceptibility determinations 

 have been attempted. 



"Immediately after section" in these series means that as soon 

 as the cutting of the series of pieces was completed they were 

 placed in KCN, Since the preparation of the series requires 

 from ten minutes to an hour according to the size and number 

 of pieces the first pieces cut remain in water for some time before 

 being placed in KCN. It was ascertained, however, that this 

 made no difference in the results since the susceptibility does not 

 change appreciably during several hours after section. In nearly 



