THE TABLES: EXPLANATORY 



9 



is inserted a tight-fitting mouthpiece (indiarubber tub- 

 ing) 7 or 8 cm. (3 in.) in length and about 2 cm. in diam- 

 eter. After use these mouthpieces should be placed in a 

 soluton of 1 per cent, carbolic acid, rinsed with water, 

 and dried before reinsertion into the tube. A fresh mouth- 

 piece should be used for each sub j ect. The sub j ect should be 



seated on a high stool, with ._.^ , , 



his back straight, opposite 

 the spirometer (Fig. 3), the 

 dial being so placed that he 

 cannot see the readings. 

 This is done for the pur- 

 pose of keeping him in 

 ignorance of the readings 

 while being examined, as it 

 is found that any such 

 knowledge tends to inter- 

 fere with the accuracy of 

 the results. The neck, chest 

 and abdomen must be free 

 from any obstruction to 

 free movement, such as 

 collar, belt or stays. The 

 subject is asked to fill the 

 lungs to the maximum 

 capacity, then the nose is 

 held with one hand, the 

 mouthpiece is placed well inside the lips with the other 

 hand in such a manner as to prevent any escape of air 

 round it. He now blows steadily into the tube, and emp- 

 ties the lungs as completely as possible into the spiro- 

 meter, being encouraged during the last period of expira- 

 tion to make the utmost effort to expel all air from the 

 lungs. The readings are given in litres and decimals of 

 litres, to be read directly from the dial. After each expira- 



FIG. 3. Testing the vital capacity. 



