REACTIONS OF FROGS TO CHLORIDES 607 



table 1, in that ammonium and potassium at least fall close to- 

 gether in their reaction-times. 



Table 3 shows that with all four frogs (I-L) potassium chloride 

 was more stimulating than ammonium chloride; the former is 

 represented by an average reaction- time of 1.84 seconds, the latter 

 by one of 3.31 seconds. In other respects the sequence of the 

 salts is the same as that shown in table 2, in that the two remain- 

 ing salts follow those just mentioned in the order sodium (5.91 

 seconds) and lithium (9.98 seconds). Not all determinations 

 at 1 m. concentration were as uniform as those shown in table 

 3. Thus, in a second series of tests at this concentration much 

 irregularity was found. This is shown in the records of this series 

 in table 4. 



Notwithstanding the irregularities in table 4, the general aver- 

 ages show the same sequence as in table 3. Thus potassium chlo- 

 ride has the shortest reaction-time (6.62 seconds), and this is fol- 

 lowed in sequence by ammonium (10.80 seconds + 1 N.R.) so- 

 dium (34.43 seconds + 3 N.R.), and lithium (46.97 seconds -f 

 6 N.R.). In this table, moreover, the grouping characteristic 

 of table 2 also occurs; namely, potassium is paired with ammonium 

 and sodium with lithium. 



The weakest solutions of the salts tested were m./2 and the 

 reactions at this concentration are given in table 5. 



From table 5 no reliable averages can be computed because of 

 the large number of failures to react. It will be seen that these 

 records of "no reactions" are most numerous for sodium (16) 

 and lithium (17), while potassium shows none and ammonium 

 six. Judged from the standpoint of the numbers of failures to 

 react, the four salts, beginning with the most stimulating, form 

 the same series as that seen at concentration 1 m. : namely, potas- 

 sium, ammonium, sodium, and lithium. It is also to be noticed 

 that they fall again into two gcoups — potassium and ammonium : 

 sodium and lithium. 



As a summary of the experiments thus far described, the aver- 

 age reaction-times, etc., for the four salts at the various concen- 

 trations used are given in table 6. 



