570 Clironicles of Science. [Oct., 



trive an instrument which should do tliis, but Dr. Saunderson has 

 certainly improved upon all previous attempts. A large square 

 pair of cahpers made of steel forms the part of the instrument 

 which grasps the chest, and which can be moved or adjusted to any- 

 particular size. The movements of the chest are made to press 

 against a spring placed inside the arm of the calipers, and by the 

 movement of the spring an india-rubber sack containing air is com- 

 pressed. By a well-known and most ingenious device the compres- 

 sion of the air in the first sack is communicated through an india- 

 rubber tube to a second larger sack placed at a convenient distance, 

 and there the motion is transferred to a dehcately-balanced lever, 

 which being furnished with a brush and ink at its long extremity, 

 writes off the movement on a regularly rotating cyhnder. The 

 advantage of this instrument is that it gives the whole movement 

 of the chest in one line — the wall of one side of the thoracic cavity 

 acting as a fixed surface in consequence of the calipers being applied 

 to opposite sides. An important feature is, that so delicate is the 

 spring and elastic sack apparatus, that the instrument acts as a cardio- 

 graph as well as a recorder of respiratory movement. The con- 

 sequence is that the tracings from the revolving cylinder present 

 two sets of curves : a large series, belonging to the movement of the 

 thoracic walls ; and a smaller set, due to the heart's impulse. Thus 

 by this instrument one is enabled most clearly and satisfactorily to 

 observe the relations of these two sets of movements and their 

 interaction. Dr. Saunderson finds that this instrument confirms 

 the observations which he formerly made with less satisfactory 

 apparatus. 



The Movement of the Wings of Insects in Flight. — M. Marey, 

 perhaps the most original physiologist which France has produced 

 in our time, has apphed himself to the study of the movements of 

 the wings of insects during flight. By gilding the tips of the 

 wings of a hymenopterous insect, he was able to render it sufli- 

 ciently brilliant to permit the eye to follow its movement, and he 

 perceived that the tip of the wing described a figure of eight in its 

 upward and downward movement. By applying a piece of sooted 

 glass to the wing, he was able to get this movement marked oft' on 

 a piece of glass. Now, to describe such a curvature combined with 

 the flapping movement, supposing the wing to be a rigid body, 

 would, M. Marey demonstrates, require a most complex arrange- 

 ment of muscles, especially to produce such a movement vnth. the 

 great rapidity with which it occurs in the insect's wing. But the 

 fact is that this " fefithering " action of the wing is due merely to 

 the up and down movement of the wing, coupled with its peculiar 

 form and elasticity. M. Marey has made a model with wings, 

 having one side rigid and the other tense but elastic, and he finds 

 that on imparting a simple movement to these wings at their point 



