SCOTT, STUDY OF CHANGES IN MUSTELVS CANIS 55 



was repeated five times. The average results equaled .0253 parts chlorine 

 per 100. This is more than twenty times as much CI as is present in the 

 fresh water of Woods Hole. In a second experiment carried on in the 

 same way, two fishes were immersed in four liters of fresh water. After 

 death, the water was evaporated down to the volume of one liter and 

 aliquot portions of this showed the presence of .68 gms. CI in the water, 

 or .01708 gms. chlorine per 100. This value is nearly twenty times the 

 amount of chlorine found in the fresh water. In these experiments there 

 were only two possible sources of the chlorides. One was the skin; but 

 in view of the thorough washing of the external surface in fresh water 

 this does not appear to me a probable source. The other was the gill 

 membranes. Diffusion through these structures seems to afford the 

 logical explanation of the presence of the salts in the water of immersion. 



Effects of Immersion in Fresh Water on Blood Pressure^ 



Respiration and Heart Beat ' 



The effects of immersion on blood pressure are not so marked as on 

 respiration and heart beat. In general, however, it can be said that from 

 the time the fresh water is turned into the tank the blood pressure falls. 

 The variations in blood pressure were recorded in the following manner : 

 After a fish had been pithed, the tail was removed and a canula filled 

 with a solution of sodium carbonate was inserted in the caudal artery.. 

 The fish was then placed in a tank of running sea-water. The canula was 

 then connected with a recording tambour also filled with the sodium 

 carbonate solution. The lever of the tambour recorded the blood pressure 

 and the heart beats on a slowly moving drum. After a normal record 

 had been obtained the fresh water was turned on. The fall in blood pres- 

 sure varies in individuals, and appears to be correlated with respiratory 

 rate and heart frequency. The blood pressure rises at times, but soon 

 falls to its former level. This momentary variation is also connected with 

 the variations in the heart beat. In three experiments at the time of 

 death in fresh water, i. e., when respiration had permanently ceased, there 

 was a fall in blood pressure of about 30 per cent from the normal. Fig. 

 10 shows the change in blood pressure of Musiehis from the time of im- 

 mersion in fresh water at 9.50 a. m. until its death at 11.15 a. m. 



Immersion in fresh water results in the gradual cessation of respira- 

 tion. For example, in one case there were 59 respirations per minute at 

 the time when the sea-water was changed to fresh water; there were 61, 

 four minutes after; 60, eight minutes after; 56, twenty-two minutes 

 after; 46, thirty-one minutes after; 33, thirty-seven minutes after; 31, 

 forty-two minutes after; 43 very feeble respirations, forty-eight minutes 



