DR PETTIGREW ON THE PHYSIOLOGY OF WINGS. 



429 



shown in the figures, I apply to each of the pieces at intervals tapering elastic 

 curved reeds (o, p, q, fig. 68), the reeds radiating in the direction of the tip of 

 the wing, and in such a manner as to confer a certain degree of spirality upon 

 it. I then cause elastic substances (h i, j k, of figs. 67 and 68,) to extend 

 between the pieces (a, d, g). The covering is then added in one piece if a bat's 

 wing is desired, and in several (see valvular wing, fig. 65, page 425,) if the more 

 highly differentiated wing of the bird is aimed at. 



jc-\- 



Fig. 67. 



d I 



Fig. 68. 



The covering may consist of a thin layer of india-rubber, silk, linen, or any 

 other flexible material. 



To the inner extremity of the distal reed (/) I attach a cord or wire, and 

 this cord or wire (/, m, n,) I pass through an aperture in the outer extremity (c) 

 of the proximal reed. I then fix the free end of the cord to a loop in the 

 cylinder (vide q of fig. 69, p. 430), from which the wing receives its movements 

 by a direct piston action. 



The arrangement is represented at fig. 69, page 430. 



When the wing is elevated from B to A (fig. 69) by the direct action of the 



* Figures 67 and 68. Wing made to close or fold during the up stroke, and to open out or expand during the down 

 stroke. 



At fig. 67, the wing is represented as folded upon itself, x Universal joint at root of wing, a Proximal portion 

 of wing, d Central portion of wing, g Distal portion of wing, b Joint uniting proximal and central portions of wing. 

 e Joint uniting central and distal portions, h i, j k Sheet of elastic substance which when contracted as represented, 

 tends to approximate the proximal (a), central (d), and distal (</), portions of wing. I, m, n A cord or wire fixed at 

 /and running through an aperture at c. If this cord be rendered taught (provided the root of the wing (x) is fixed in 

 its socket), it causes the proximal (a), central (d), and distal {()) portions of the wing suddenly to dart out and arrange 

 themselves in a nearly straight line as shown at a, d, g of fig. 68. 



At fig. 68 the wing is represented as fully extended or spread out. The lettering is the same as in fig. C7. o, p, q 

 Ribs or stays of the wing which support the covering or curtain. 



