60 



ANNALS NEW YORE ACADEMY OF SCIENCES 



possibly an instance of reflex inhibition of the heart beat due to the 

 cardiac-inhibitory center being stimulated by impulses from sensory 

 nerves; but the heart gradually recovered the force and rate it had prior 

 to the convulsive movement, and the respiratory spasm ceased. 



During the twenty minutes after immersion, there occurred about ten 

 very marked respiratory spasms with their accompanying effects on the 

 heart. Twenty or more took place during the second twenty minute 

 period. After this they diminished in number and force, ceasing almost 

 entirely about the 70th minute. Some respirator}- convulsions took place 





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Fig. 13. — Showing changes in Mood pressure and heart heat of Squalus due to transfer- 

 ence from harbor tcater to fresh water from 11.06 A. M. to 3.56 P. M. 



after regular respirations had ceased. Fig. 12 shows the changes in tlie 

 character of the heart beat of this specimen. 



The case with Squalus acanthias studied at the New York Aquarium 

 during the early winter, December, differs from that of Mustelus. The 

 water in which these fishes had been kept had a temperature of about 

 12° C. Moreover, the fishes, as has already been described (p. 32), had 

 been living in a diluted sea-water for some time. The rat^ of the heart and 

 of the respiration was much lower than in the case of Mustelus in summer. 

 Moreover, it was observed that the fishes lived longer after the fresh water 

 was turned on than was the case with Mustelus. One specimen was under 

 observation for five and one-half hours, during which a record was kept 



