move//3i 

 it is f/n 

 it ai//th 



BY DR. BURDON-SANDERSON. 249 



regular intervals, which correspond with the previous frequency 

 of the respiratory acts. In the absence of self-acting apparatus, 

 the best instrument to use is the caoutchouc blower and ex- 

 panding regulator sold by Messrs. Griffin for working the gas 

 blow-pipe (see fig. 221). The blower is worked by means of a 

 squeezer. It consists of an oblong board or lever, 16 inches 

 long, 3 inches wide, and j inch thick. This board is hinged in 

 the middle to a fulcrum, in such a way as to admit of a see-saw 

 The fulcrum is firmly screwed to the table. When 

 use, the blower is placed under one end, i. e., between 

 the table, the degree of compression being limited by a 

 str/ig cord attached at the opposite end to the table. By 

 varying the length of the cord, the quantity of air injected at 

 each stroke is regulated. The blower communicates with the 

 respiratory cavity by a trachea! canula. No valve is required, 

 the expired air passing out freely during the intervals between 

 each injection and its successor, by a hole in the tube. The 

 quantity of air discharged by the blower at each stroke must, 

 therefore, considerably exceed the quantity which is required 

 for respiration. This contrivance can be worked with much 

 less fatigue than bellows. The time must be regulated \>y a 

 metronome. The self-acting apparatus consists of two parts 

 a constantly acting blower or expirator, and an arrange- 

 ment for interrupting the current of air at regular intervals. 

 The best constant blower is that known as Sprengel's blowpipe, 1 

 the structure of which will be understood at once from fig. 222. 

 The essential part of it is the vertical tube J, with its branch 

 e, the lower end of which opens in*o a bottle having two other 

 openings. Of these, one, which communicates with the top of 

 the bottle, is for the efflux of air; the other, near the bottom, 

 for the escape of water. If a continuous current of water is 

 caused to pass through rf, e remaining open, it carries with it a 

 quantity of air which passes down into the bottle; and if the 

 screw clamp c is so adjusted as to allow the water to flow out 

 of the bottle at the same rate that it flows in from 0, the water 

 in the bottle remains at the same level, and a constant stream 

 of air escapes from b. The interruption of the stream of air so 

 produced is effected by means of an electro-magnet, which is so 

 arranged that each time the voltaic current is closed, a weight 

 bj- which the tube is compressed is lifted, and thus air is in- 

 jected so long as the magnet is in action. The voltaic current 

 raay be closed aud opened either by a metronome or by the 

 mercurial breaker, shown in fig. 22IJ. Two copper wires, one 

 of which is connected with the battery, the other with the mag- 

 net, run along the top of the wooden bridge, nearly meeting at 



1 A somewhat more complicated apparatus ( Waxxerluftpumpc zur 

 Erzeugung comprimirter Luft) is sold by Desaga of Heidelberg. 



