Dr. W. H. Stone on Wind-pressure in the Human Lungs. 113 



VI. Barometer 2' 1 millims.: — 



At division 35 2*601 71 *■«■„„„ o.^ais 

 „ 30 2-60731 Mean 2 60i °- 



Renieasured. 

 At division 35 2*6160 "1 , T onno 

 „ 30 2-6320J- Meau 2 019 °- 



It may be mentioned incidentally that connexions for appa- 

 ratus may be conveniently made by means of ball-and-socket 

 joints of glass. The ball is made by thickening a piece of tube 

 in the blowpipe-flame, and the socket by cutting in halt a thick 

 bulb blown on a glass tube. The ball is then ground into the 

 socket by means of emery and solution of soda, and afterwards 

 polished with rouge and soda solution. When slightly greased 

 and with a small quantity of mercury in the cup, a joint is ob- 

 tained which is perfectly air-tight and flexible*. 



XVII. On Wind-pressure in the Human Lungs during Perform- 

 ance on Wind Instruments. By Dr. W. II. Stone f. 



THE object of these experiments was originally physiological. 

 It had been stated by many writers that the forced expi- 

 ration employed in playing tended to produce emphysema of 

 the lungs ; but the real amount of such pressure had never 

 been measured. 



The facts elicited had also an interest of a purely physical 

 character, which was the principal cause of their being brought 

 before this Society, although, the writer of the paper remarked, 

 it was on the border-ground between two great subjects of study 

 that new phenomena were often to be looked for. 



The experiments were two in number. The first aimed simply 

 at measuring, by means of a water-gauge, the extreme pressure 

 which could be supported by the muscles of the lips, both in 

 trained musicians and in persons unaccustomed to the con- 

 tinuous exercise of these organs. The difference between dif- 

 ferent individuals was very great, some untrained persons 

 having naturally considerable muscular power. About 6 feet 

 of water was the ordinary maximum when a small tube was 



* Since the above was written Dr. Sprengel has pointed out that Mr. 

 Hartley (Proc. Roy. Soc. vol. xx. p. 141) has described as a "Sprengel 

 joint" a connexion between two glass tubes made by grinding a conical 

 tube into a conical cup and placing mercury or water in the cup. The 

 difference between this and the one above mentioned is obvious : the 

 former is quite rigid, the latter perfectly flexible. 



t Read before the Physical Society, April 18, 187-1. Communicated 

 by the Society. 



Phil. Mag. S. 4. Vol. 48. No. 316. Aug. 1874. I 



