FUNCTIONS OF SWIMBLADDER OF FISHES. IOQ 



In Fig. 9 it will be seen that normal blood is reduced (the bubbling 

 was more rapid and the temperature higher) from 100 per cent, 

 to 35 per cent in fifteen minutes, while when it contained M/i^o 

 HCL and M/I2O lactic acid the same reduction was effected in 

 about six and one half and seven and one half minutes respec- 

 tively. Thus it becomes evident that the "reaction," namely 

 the hydrogen ion concentration of the blood effects the reduction 

 of the blood ; the amount of dissociation of the oxygen from the 

 oxyhemoglobin is in proportion to the increase in the hydrogen 

 ion concentration. 



How may these facts be correlated with the conditions found 

 in the swimbladder of fishes? The abundant supply of blood 

 furnished to the swimbladder by means of the rete mirabile has 

 already been described. The question arises is the gland which 

 includes the rete mirabile able to force the vascular system to 

 give it the oxygen which it may require in order to maintain a 

 pressure in the swimbladder equal to that at the depth to which 

 a fish is subjected? Does it perform this function by secreting 

 substances causing a dilatation of the blood vessels of the rete 

 mirabile, thus producing an increased flow of blood to the gland, 

 or do these substances accelerate the reduction of the oxy-hemo- 

 globin, or is it a combination of both these processes? 



An attempt was made to determine the hydrogen ion con- 

 centration changes that might take place in the swimbladder. 

 In making the tests fish were quickly removed from the aquaria 

 and the spinal cord severed just posterior to the brain. The 

 body cavity was opened, the swim bladder gland raised by forceps 

 and cut free from the body, as little time elapsing as possible 

 during the operation. Care was taken not to get any of the body 

 secretions or fluids on the gland. The gland was then placed in 

 a small vial containing about five cubic centimeters of distilled 

 water, which was free from carbon dioxide, which had been 

 previously weighed. The vial was again weighed and the weight 

 of the gland computed. After standing for a definite length of 

 time (see Tables IX. and X.) colorimetric determination of the 

 hydrogen ion concentration was made. The vial was only 

 slightly agitated during the period of standing, in order to keep 

 the gland intact. Three cubic centimeters were pipetted off for 



