45, CORNHILL, B.C., AND 122, REGENT STREET, W., 



LONDON, 



499 



FIG. 3091. 



FIG. 3101. 



3091 Portable Medical Spirometer, Patent (fig. 3091). This instrument from its 

 very small size will be found a very useful addition to the consulting room 

 of the physician, and to the physiological laboratory. The measurement 

 of the vital capacity is obtained by measuring the velocity of the expired 

 current during the time of expiration, and the instrument is arranged so 

 as to reduce the velocity of the current to Cubic Measure. 

 Each Spirometer is experimentally Tested by means of a vessel filled with air 

 immersed in water, the cubic contents of this vessel being known ; the air 

 is made to pass through the Spirometer at a pressure of six inches of water ; 

 the Spirometer is then regulated to show the cubic contents of the vessel. 

 By this means it is found the error of the instrument seldom amounts to 

 more than 2 per cent. 



DIRECTIONS FOR USE. Each instrument is provided with a condenser, which 

 should be placed in a tumbler of cold water ; the tube with the mouth-piece must be 

 fixed to the orifice of the condenser, marked " in" and the instrument to that 

 marked " out." The hands must then be set to zero by turning the milled head, at 

 the same time pressing the spring forward. The patient is directed to take a deep 

 breath, and then to expire steadily through the mouth-piece for as long as possible. 

 The index hands register the number of Cubic Inches of Air expired. 



The use of the condenser is to prevent the moist air entering the instrument. 

 After repeated use it is necessary to empty the accumulated water. This is done 

 by disconnecting the instrument and inverting the condenser. Price 4 10 



Table of the Vital Capacity of the Lungs, compared in Health and in Consumption, 

 at 60 Fahrenheit, upon 5,000 Cases (Male). 



2K2 



