12 hougk: 



Frog No. 7 was made reflex, and the right brachial 

 and sciatic plexuses were stimulated, with two min- 

 utes of rest alternating with two minutes of stimula- 

 tion, for two and a half hours. The stimuli were 

 regulated so as to be as strong as possible without 

 causing reflex contractions of the muscles of the other 

 side. At the end of this time but slight muscular 

 contractions could be obtained from the arm or leg of 

 the right side, and no reflex contractions whatever 

 from stimulating the skin of this side, while stimu- 

 lating the skin of the left side gave normal reflex con- 

 tractions in that side. 



Sections of the ganglia from the two sides show 

 marked differences. Perhaps the most pronounced of 

 these is a difference, noted independently by a number 

 of observers, viz. that the nuclei appear shrunken in 

 the stimulated ganglia. This led to a series of meas- 

 urements, the results of which are given in the fol- 

 lowing table. The nuclei were measured, long and 

 short diameters, in sets of one hundred, fifty stimu- 

 lated and fifty unstimulated being taken from as 

 nearly corresponding sections as possible of the two 

 ganglia. A definite rule precluded any willful selec- 

 tion of the cells to be measured, the rule being that 

 only nuclei containing nucleoli should be measured, 

 and that all such should be taken in the order of their 

 occurrence in the section. The measurements were 

 made to the nearest // under a magnifying power of 

 Leitz, Oc. 3, Obj. 7 (=600 diameters). 



Table I.' 

 Frog No. 7. Made reflex, stimulated 2} hours, in- 



'The tables have been recomputed, and so differ slightly from 

 those ill the preliminary communication (Am. .Tour. Psyciioi,., Vol. 

 I, J). 479 ff.). The difference is due to using the square root of the 

 average surface of the nuclei, instead of the arithmetical mean, for 

 the mean diameter. 



