of Edinburgh, Session 1870 - 71 . 
337 
Professor Marey, by employing a sphygmograph similar to 
that used for ascertaining the state of the pulse, succeeded in 
causing the wings of insects and birds to register their own move- 
ments. He says : — “ But if the frequency of the movements of 
“ the wing vary, the form does not vary. It is invariably the same ; 
“ it is always a double loop , a figure of 8. Whether this figure be 
“ more or less apparent, whether its branches be more or less equal, 
11 matters little; it exists, and an attentive examination will not fail 
“ to reveal it.” * 
The subjoined are a few of the results obtained by the author in 
the course of his numerous observations and experiments: — 
The wing is of a generally triangular form. It is finely gradu- 
ated, and tapers from the root towards the tip, and from the anterior 
margin towards the posterior margin. It is likewise slightly twisted 
upon itself, and this remark holds true also of the primary or rowing 
feathers of the wing of the bird. The wing is convex above and 
concave below, this shape, and the fact that in flight the wing is 
carried obliquely forward like a kite, enabling it to penetrate the 
air with its dorsal surface during the up stroke, and to seize it with 
its ventral one alike during the down and up strokes. The same re- 
mark applies to the remiges or rowing feathers of the wing of the 
bird. 
The wing is moveable in all its parts; it is also elastic. Its 
power of changing form enables it to be wielded intelligently, even 
to its extremity ; its elasticity prevents shock, and contributes to 
its continued play. The wing of the insect is usually in one 
piece,f that of the bat and bird always in several. The curtain of 
the wing is continuous in the bat, because of a delicate elastic 
membrane which extends between the fingers of the hand and along 
the arm ; that of the bird is non-continuous, owing to the presence 
of feathers, which open and close like so many valves during the up 
and down strokes. 
The posterior margin of the wing of the insect, bat, and bird, is 
rotated downwards and forwards during extension, and upwards 
* Revue des Cours Scientifiques de la France et de l’Etranger, p. 252. 
20th March 1869. 
f The wings of the beetles are jointed, so that they can be folded up 
beneath the elytra or wing cases, 
