To prevent the handle bending over, solder round the pivot hole 3/4 inch of brass tubing, fitting the pivot closely.
Tests.—Grip tests should be made with each hand separately. The baseboard should lie flat on a table or other convenient support, and be steadied, but not pushed, by the hand not gripping.
Twisting tests may be made inwards with the right hand, and back-handedly with the left. The apparatus is stood on edge, square to the performer, resting on the horns of A and a support near the balance.
Finger tests are made by placing the thumb on the front face of B, and two fingers on the farther side of the lever, one to the left and the other to the right of the tail of the balance.
XXX.
LUNG-TESTING APPARATUS.
The capacity of the lungs, and their powers of inspiration and expiration, can be tested by means of easily constructed apparatus which will interest most people who are introduced to it. The reduction of the capabilities of the lungs to figures affords a not unprofitable form of entertainment, as even among adults these figures will be found to vary widely.
Air Volume Measuring.—The air which the lungs deal with is scientifically classified under four heads:
1. Tidal air, which passes into and out of the lungs in natural breathing. About 30 cubic inches in an adult (average).
2. Reserve air, which can be expelled after a normal expiration. About 100 cubic inches.
3. Complemental air, which can be drawn in after a normal inspiration. About 100 cubic inches.