ARTIFICIAL RESPIRATION MACHINE 



473 



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r Interrupting^ 



e r 

 K 



Fig. 360. Diagrammatic representation of an artificial respiration machine. The 

 % horse power motor turns a. rotary air pump. Crowell's rotary air pumps (for both 

 pressure and vacuum) are advised but other forms of pumps are on the market. The 

 second size (2-A) is sufficient for 10 or 20 dogs at one time but a l /y horse power motor 

 should be used as the interrupting air valve should also be operated by power from the 

 motor. I2y opening valves A, tf , with valves C, D, closed, a vacuum will be produced 

 in the tank when the pump runs. By reversing all these valves positive pressure will be 

 produced in the tank. These valves should be lever gate valves (Fig. 362) which can 

 be opened or closed instantly. Thus changes from positive to negative pressure (or the 

 reverse) can be made in about one second without stopping the pump. In some cases it 

 is possible to accomplish this by reversing the motor. From the tank air is piped (three- 

 fourths or one-half inch gas piping) to all parts of the laboratory. Two main lines of 

 piping around the room are shown in the figure. The feed pipe from the tank divides 

 into two parts and each of these two divisions supplies both of the main lines of piping 

 around the room. The purpose of this is to give an opportunity for one set of pipes to 

 carry a constant supply of air (either positive or negative) while the other line may be 

 carrying an interrupted current (either positive or negative). If two tanks are used both 

 positive and negative pressure may be had simultaneously, but with only one tank as 

 illustrated here only one pressure (either positive or negative) can be had at one time. 

 The pipe carries an interrupting valve (), (lever gate valve. Fig. 362) which is inter- 

 rupted at regular intervals (from 25 to 40 times or more per minute). The large (8 or 

 10 inch) wheel .R, turns the spindle holding the cone pulleys, 1, 2, 3, which in turn 

 carry the belt (one-inch flat leather tied together with belting wire) which turns the 

 wheel P. The wheel P, is 8 or 10 inches in diameter and has a four-inch face. Thus 

 the flat (one-inch) belt can be placed on either small pulley and still be slipped along the 

 surface of the wheel P. On the outer edge of P, is a hill-shaped lug which raises and 

 lowers the pulley L, at each revolution of P. It is important for L, (which works the 

 lever M, and the bar TV, which operate the lever gate valve E) to be raised and lowered 

 quickly but noiselessly, hence the hill-shaped elevation up and down the sides of which the 



