208 THEO. C. BURNETT. 



ity was about nineteen hours, nine of which were spent in 

 vigorous activity. 



These three experiments were selected because they came in a 

 series, and it so happens that it includes two of those that are the 

 least typical of any. Exp. Jan. 28/'o7 as has been said, lived for 

 a much shorter time than usual, while in exp. Feb. 4/' 07 the 

 turtle was blind and sluggish ; when the plastron was removed 

 the heart was not contracting, nor did the auricles contract until 

 they were suspended. 



Exp. Feb. 8/'oy ; temperature 17-21 C. Two strips of the 

 turtle's ventricle were prepared and exhausted in NaCl. Strip 

 A was then transferred to dilute sea water. At the end of six 

 minutes it began contracting vigorously with a much greater 

 amplitude -than in NaCl ; at first with a rate of six per minute, 

 but soon dropping to one in two or three minutes. In about 

 fifteen minutes it ceased abruptly and remained perfectly quiet 

 for about three quarters of an hour. It was then transferred to 

 " Ringer," and in seven minutes began giving maximum contrac- 

 tions with a somewhat irregular rhythm ; there would be a group 

 of six to eight per minute, then a pause for half a minute and 

 then another group. When it had been contracting in this way 

 for one and one half hours it was again transferred to sea water. 

 It was then registering on a twelve hour drum and the rate was 

 not taken ; but in fifteen minutes it again ceased abruptly and 

 remained perfectly quiet for between five and six hours. Again 

 transferred to " Ringer," it remained quiet for half an hour and 

 then began to contract vigorously, but with gradually diminishing 

 amplitude, and during the night it ceased. Next morning it 

 failed to respond to stimulation. Strip B was used as a control. 

 After NaCl exhaustion it was placed in " Ringer" instead of sea 

 water, and recovered at once with a rate of sixteen gradually drop- 

 ping to twelve per minute. The subsequent course of this strip 

 was similar to strip A ; when A was in " Ringer," B was in sea 

 water and vice versa. When A was active in " Ringer," B was 

 quiescent in sea water. The record of the auricles was lost after 

 seven hours. 



Having ascertained the influence of dilute sea water upon the 

 different parts of the heart separately, the whole heart was sus- 



