164 ANNALS NEW YORK ACADEMY OF SCIENCES 



This experiment shows that an inflated rubber balloon can take the 

 place of all the abdominal organs in respect to noise-production; although 

 it does not prove that these organs may not play some part in the normal 

 mechanism. 



To determine whether there is any experimental basis for the view held 

 by Jordan and Evermann, viz: that the drumming is produced by forcing 

 air from the air-bladder into one of the lateral horns, the following experi- 

 ments were undertaken. 



Experiment V. — An incision about one inch long was made in the mid-ventral 

 line of a male squeteague. The air-bladder was ligatured in the middle, thus sepa- 

 rating the organ into two chambers, — the anterior containing the lateral horns, 

 and the posterior remaining a simple closed ca\'ity. Drumining, however, went on 

 as in nonnal animals. 



a. The part of the bladder posterior to the ligature was punctured. The 

 drumming continued only in the region of the anterior part of the bladder, which 

 remained inflated. 



b. Another animal was prepared in the same way, and the part anterior to the 

 ligation was punctured. The drununing continued only in the region of the posterior 

 portion of the bladder, which remained inflated. In this part of the bladder there 

 are no lateral horns. 



c. The posterior end of the bladder was then folded into the anterior part of the 

 abdomen. The drumming noise then came from the anterior part of the abdomen 

 in the region of the inflated half-bladder. 



d. The anterior half of the bladder was amputated, leaving the posterior part 

 still inflated. This was inserted at different places and the drumming noise occurred 

 wherever this part of the bladder was placed. 



Experiment VI. — An incision was made in the mid-ventral line of a large 

 "drummer," about half way between pectoral and anal fins. At the right angles 

 to this incision, longitudinal incisions were made on both sides, extending nearly to 

 the region of the kidney. These incisions were made through the drumming muscles. 

 The air-bladder and -vascera were lifted up with forceps, and the remaining part of 

 the drumming muscle and central tendon was cut. This separated the entire muscle, 

 tendon and insertion into halves — an anterior and a posterior part. The drum- 

 ming still continued on both sides of the bisection. In order to show this still more 

 completely, the anterior half of the abdomen was raised by inserting two fingers, 

 which prevented the drumming in this (anterior) part, while the posterior gave the 

 same characteristic noise. Next, the posterior half of the abdomen was raised in 

 the same maimer, and the drumming stopped in the posterior part but continued 

 in the anterior. Upon removing the fingers, the noise continued as in normal ani- 

 mals. 



a. The air-bladder was ligatured in the same place as the bisection of the muscle. 

 The drumming occurred as before. Again the anterior and the posterior parts were 

 in turn raised, and the drumming was made to occur in either part at ^nll. 



The two experiments V and VI, as well as the previous ones, prove 

 conclusively that the lateral horns have nothing to do with producing the 



