Y. Henderson 49 
Apparatus for gas analysis has been discussed in the fourth 
paper of this series. In addition td a gas analyzer one needs a 
large graduated spirometer, a flexible tube, nose clip, and a 
mouthpiece with inspiratory and expiratory valves. 
The spirometer shown in Fig. 1 is a simple form which has proved 
easily constructed and sufficiently accurate in use in this laboratory. 
The lower container consists of a common galvanized iron ash can. The 
tube is iron pipe (bore 1 inch) with a brass cock such as is used on steam- 
pipes. A round hole (2 inch) is bored in the side so that it serves as a 
3-way cock. A disk of galvanized iron is fastened near the top of the 
pipe and lies just below the surface of the water with which the can is 
filed. This prevents the diffusion of any considerable amount of CO, 
into the water. The bell or floating container is made of tin. It should 
be as nearly as possible of exactly the same diameter everywhere (this 
requirement is easily met by any competent tinsmith). The cord to the 
_ counterpoise weight runs over window sash pulleys. The rise of the bell 
of the gasometer is measured by a self-winding steel mm. tape measure 
of which the case is fastened to the cross bar of the wooden frame. The 
volume of the bell per mm. rise is merely its diameter multiplied by mr?. 
The error which would occur if the dead space of the apparatus were filled 
with fresh air is eliminated by running a fore period in each experiment 
during which the gasometer is partly filled with expired air. Just before 
the period of the observation it is emptied through the side hole in the 
brass cock, thus leaving the dead space of the apparatus (tube and top of 
bell) filled with expired air. 
To connect the mouthpiece and the spirometer the best tubing is the 
corrugated rubber used in mine rescue apparatus, but this is expensive 
and a very satisfactory substitute is afforded by a piece of vacuum cleaner 
tubing, which can be ordered in the proper length (2 or 3 feet) with heavy 
rubber nipples at the ends, from any vacuum cleaner shop. The standard 
rubber and metal mouthpiece has mica disk inspiratory and expiratory 
valves attached to it.} 
A form of valve which has proved convenient has recently been 
devised at the University of Minnesota by Professors A. D. Hirsch- 
felder and E. D. Brown. By their kind permission a diagram 
of two of these valves arranged for inspiration and expiration on 
a T-tube is shown in Fig. 2. Each valve is made of a large tin 
1 These valves on a metal mouthpiece, the rubber mouthpiece and cor- 
rugated tube and nose clip, as well as the Douglas bag with a large alu- 
minum 3-way cock and other similar equipment are obtainable from 
H. N. Elmer, 1140 Monadnock Building, Chicago, the agent for Siebe, 
Gorman & Company of London. 
THE JOURNAL OF BIOLOGICAL CHEMISTRY, VOL. XXXIII, NO. 1 
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