LECT. II.] RESPIRATION OF A TURTLE. 57 



of blood-vessels acts as a respiratory organ. He further states that 

 in the pharynx are many fringe-like processes which resemble the 

 inner gills of tadpoles, and probably have the same function, 

 although no mention is made as to the method of their use. 



"In 1878, while watching a soft-shelled turtle from Cayuga Lake, 

 confined in a glass aquarium, it was observed that the throat and 

 the floor of the mouth became alternately swollen and collapsed, 

 while the turtle was completely immersed in the water. The 

 appearance was very much like the respiratory movements of a 

 frog in the air. As no air escaped from the turtle, the bulging 

 of the throat and mouth must be caused by filling the mouth and 

 pharynx with water, and expelling it, or the air must be forced into 

 the mouth from the lungs and then forced back into the lungs, as 

 is done sometimes by men when swimming under water. 



" In order to determine whether or not water was taken into the 

 mouth and expelled, the bottom of the aquarium was covered with 

 fine sea sand, and the observations were made when the animal was 

 resting quietly on the sand. 



"At the beginning of the movement, the mouth would slightly 

 open, and its floor would swell out, the swelling passing steadily 

 onward to the throat. After a moment of quiet, the swelling would 

 disappear in the inverse order of its appearance. 



" During the disappearance of the swelling of the throat and mouth, 

 the sand, for a considerable distance in front of the animal's head, 

 would be swept aside as by a rapid stream. The movement of 

 the sand, without the escape of air, seemed to prove conclusively 

 that the mouth and throat were alternately filled with water and 

 emptied. 



" These pharyngeal respirations, as they may be called, were very 

 regular, occurring ten or fifteen times a minute. My observations 

 were verified by Professor Wilder and several of our laboratory 

 students. 



" While, therefore, the investigations of Agassiz showed that in the 

 pharynx of the soft-shelled Turtle were organs apparently suitable 

 for aquatic respiration, the observations here recorded of the 

 rhythmical bathing of these organs with fresh water seem to make 

 the evidence complete, that a true aquatic is combined with an 

 aerial respiration. 



