MASCHA | STRUCTURE OF WING—FEATHERS 5 
fibers on each side of the secondary quills vexillum primitif. After 
him Strasser (1885, p. 197) noticed these structures, and introduced 
the expressions secondary quills and secondary vanes, to distinguish 
the former from the primary quill and the latter from the primary 
vanes of the whole feather. 
The secondary quills arise dorsally from the sides of the primaries, 
and extend obliquely outward. The angle between them and the 
primary quills is about 50° in the arm-remiges and changes but little 
in the whole length of these feathers in both vanes. It is subject to 
greater variations in the hand-remiges. Here it is greatest at the 
base of the feather (about 50°), towards the end of the feather it 
becomes smaller, the outermost secondary quills rising from the 
primary quill at an angle of only 20-25°. In the central broadest 
part of the hand-remiges this angle is 30-40°. In the outer vane of 
the hand-remiges the angle is always smaller than in the correspond- 
ing part of the inner vane. At the distal end of the feather the 
secondary quills are curved and their tips turned in the direction 
of the continuation of the primary quill. The secondary quills are 
for the greater part of their length considerably compressed laterally, 
becoming band-like. They are highest at their origin from the pri- 
mary quill and decrease in height outwards, finally tapering to a fine 
point (fig. 12, a, b, c). 
A few words must be said here concerning the histological struc- 
ture of the secondary quills. Like the primary quill they appear 
as horny tubes (figs. 1, 2, 3, 4, Hus) enclosing a medullary sub- 
stance or core composed of large polyedrical cells filled with air 
(figs. I, 2, 3,4 Mks). Klee (1886), p. 92-30) has pointed out that 
the cortex and the core are essentially different, but that both arise 
from similar elements, at first homogeneous. Davies (1889, pp. 
588-589) has fully and clearly described this process of conversion 
of the intermediary cells into cortical and medullary substance. He 
says: “ The modification consists in a considerable increase in size 
of the central space which, in horned cells, contains the nucleus, 
combined with a change in the form of the cell.” The relative posi- 
tions of the cortex and the core are shown in the transverse sections 
of secondary quills represented in figs. 1-7, 29. 
Two types of secondary quills can be distinguished. In the first, 
which is by far the most frequent, the core is irregular, composed 
of many layers of irregularly arranged core cells and the interior 
of these secondary quills presents a honeycomb-like structure. In 
the second type, met with in the Owls and Caprimulgi (figs. 2, 4, 7, 
29), the core cells are arranged in a single vertical layer, irregularly 
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