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EXPERIMENTAL PHARMACOLOGY 



pulley L rolls. The i-ah'c E must be opened and closed Quickly. This lets a gush of 

 air enter (or leave) the main lines of piping. If these lines were very short this sudden 

 gush of air might burst an animal's lungs. It is to be emphasized, however, that the 

 pipe lines are long (100 feet or more of piping may be used) and that the air suddenly 

 compressed in these pipes w 11 escape only gradually at the small faucets at the tables. 

 Thus the period of inflation of the lungs may be as long as the period of deflation. The 

 danger is that air may. continue to escape over nearly all the period, between each two 

 successive openings of the valve. A slowly opening and closing vah'c is nearly sure to 

 cause this difficulty. 



At F is shown a pressure regulating ralrc. The exhaust pipe leading from this 

 should pass up inside a hood-draft opening in the wall or out through a window casing, 

 etc., to the outside of the building. The valve F is a screw valve and when it is set 

 for a certain opening then the excess air compressed in the tank will constantly escape 

 at practically the same rate through the valve F. Thus the pressure in the tank is regu- 

 lated. The pressure gauge is used for this regulation. For (positive) artificial respira- 

 tion usually from 3 to S pounds pressure is needed. Blast lamps, etc., can be operated 

 by this same air system. A special (pop-off) pressure regulating valve for the tank is on 

 the market, but this valve makes a most hideous and disgusting noise in the laboratory. 

 It is better to simply let the excess air escape to the outside of the building through the 

 valve F. 



The tank need not be large. A ten or twenty gallon hot water tank is sufficient. 



The rotary pump costs about $26.00. (A smaller size, 1-A, listed at $2,0.00 may be 

 used for smaller laboratories.) A l /2 horse power motor costs from about $30.00 to ap- 

 proximately $60.00. The tank may cost from $4.00 to $8.00. If a laboratory possesses 

 fair shop facilities of its own such an air system can be installed for about $75.00 to $100.00. 

 The most difficult part is the construction of the apparatus to operate the interrupting 

 valve. This should be firmly and reliably constructed. For ten years the writer has used 

 an artificial respiration machine similar to that described above. The outfit can be 

 thoroughly recommended. 



Fig. 361. View of system of pulleys used to operate the interrupting valve. Seen 

 from above. The framework is made of gas, pipe and fittings. The cross on the right 

 hand end of the frame and the two tees on the left end are bored out to rotate on the 

 end bars. Thus the two hinges are formed. This valve operating device can also be 

 used in laboratories where compressed air from the power plant is supplied to the build- 

 ings. Hanzlik has recently described a multiple pump system for artificial respiration. 

 (See Journal of Laboratory and Clinical Medicine, 1916, i, 688.) Several artificial res- 

 piration machines using belloit's, etc.. are on the market. For student purposes these 

 should be avoided. 



Lever qate valve 



Fig. 362. Lever gate valve ( I.ukenhcimer, "Handy valve"). These are stock valves 

 and cost from 40 cents to $1.00. They are able to withstand 125 pounds steam pressure. 



