METHODS OF MEASURING RESPIRATORY EXCHANGE 51 



In certain cases, and especially when the natural respiratory 

 movements have been prevented by narcosis, a current of water must 

 be maintained to provide a sort of artificial respiration. Samples of 

 the water are then collected in front of and behind the vessel holding- 



O 



the animal, and the total quantity of water passing during a certain time 

 is measured. Arrangements of this kind have been described by 



FIG. 20. Respiration apparatus for a fish with arrangement for artificial ventilation. 



Winterstein [1908] who measured the branchial respiration of fishes as 

 separate from the total, and lately by Ege and Krogh [1914] who 

 measured the total oxygen absorption of a narcotized fish. Fig. 20 

 shows the arrangement adopted by Ege and Krogh. The water is 

 collected and measured in an inverted measuring cylinder (6) and 

 protected against contact with air by means of vaseline oil (7). 

 Samples are drawn at (8) and (9) respectively. 



