XXXHI. Respiration in abnormal media. 



/. Appliances. Three small animals; three jars or wide- 

 mouthed bottles; hydrogen generator; nitrogen genera- 

 tor; water bath; potassium nitrite; ammonium chloride; 

 operating case; dissecting boards. 



2. Preparation. Dissolve 66 grammes of ammonium chlor- 

 ide in 500 cubic centimeters of water. Dissolve 100 

 grammes of potassium nitrite in 500 cubic centimeters of 

 water. Prepare a nitrogen generator as shown in the 

 figure, using a liter flask. (Fig. 25.) 



3. Operation. 



a. Pour the two solutions into the generator; adjust con- 

 ducting tube; heat the mixture in the generator; in a 

 few minutes nitrogen gas will be given off from the 

 mixture as the result of the following reaction: 



If the jars used by the different divisions are not too 

 large the above suggested quantities of the solutions 

 will probably supply enough gas for several divisions. 

 Put an animal into the jar of nitrogen and close the 

 jar. 



b. Fill a jar full of water, displace it with hydrogen 

 gas. Put an animal into the jar and close it. 



c. Put an animal into a third jar, confining it with a 

 cloth or a sheet of rubber. Join a rubber tube to an 

 illuminating gas jet, introduce the end of the tube in- 

 to the mouth of the jar; turn the gas on for an instant 

 only. After five minutes allow another momentary 

 puff of illuminating gas to enter the jar. 



147 



