58 



ANNALS NEW YORK ACADEMY OF SCIENCES 



fishes studied. At times, the respiratory rate and heart frequency are 

 equal; but they appear to be little correlated. After immersion in fresh 

 water, there is rarely any sign of relation between the two rates. Fig. 11 

 shows the change in the character of the respirations due to the immer- 

 sion of Mustelus in fresh water. 



ili 11 



Uxi^i^vlMVWOJ^KKWJ^VKW^ 



Fig. 12. IShoiciiKj chunyes in heart heat of Alii-stclus due to immersion of fish in fresh 



water. Irregniarities represent spasmodic cardiac morements 



The effect on the heart beat of the immersion of Mustelus in fresh 

 water was studied directly in the following experiment, of which Fig. 12 

 is a record: A female Mustelus canis 79 cm. long, 1247 gms. in weight, 

 was pithed and an opening about 1 cm. square was made in the pectoral 

 arch over the pericardial cavity. A fine hook Avas attaclied to the tip of 



