4 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vor. 48 
blocks I successfully adopted the method of covering the top of the 
block with melted paraffin after each section, and congealing it by 
means of a current of cold air.1 A very oblique position of the knife 
is essential to procure good sections. In the paraffin method I 
stained with safranin before imbedding. The sections were glued 
to the slide with Schallibaum’s collodion-clove oil and cleared with 
xylol. Although thin sections could be made by this method it had 
many drawbacks. The sections frequently split, and while remov- 
ing the paraffin with xylol numerous portions of them were lost. 
By experiment I found that the splitting was almost entirely ob- 
viated by the employment of celloidin, although it is true that the 
celloidin method also presented difficulties. It is hard to make as 
thin sections of celloidin blocks as of paraffin, and staining is much 
more difficult. If one stains (with safranin) before imbedding, the 
ether extracts even the strongest stain. If one stains the sections 
after cutting, the celloidin also takes the stain. The sections were 
at first made only on the two directions parallel to one of the two 
kinds of tertiary fibers. These proved to be very instructive for 
the exact study of the tertiaries but did not throw sufficient light upon 
the structure of the secondaries. To study these, sections were 
made vertical to the secondaries, which gave the desired information 
concerning them. 
3. The Primary Quill 
The morphology of the primary quill (fig. 6, Htk)? have already 
been fully discussed. Ahlborn (1896, p. 15-16) in particular has 
given a complete description of this part of the feather, illustrated 
by.a sketch, and has drawn attention to the importance of its struc- 
ture for flight. I therefore turn at once to the description of the 
parts composing the feather vanes, beginning with the considera- 
tion of the secondary quills. 
4. The Secondary Quills 
The secondary quills are the bearers of the feather-vanes. Just 
as they themselves spring obliquely from both sides of the dorsal 
part of the primary quill, so they bear dorsally the tertiary hook and 
curved fibers. Clement (1876, p. 282) has drawn attention to this 
in a somewhat different sense. He calls the plate, composed of the 
two vanes of a feather, ve-villwm, and the vane formed by the tertiary 
*The method employed was described by Professor von Lendenfeld in 
Zeitschrift fiir wissenschaftliche Mikroskopie und mikroskopische Techmk, v, 
18, pp. 18-10. 
2For figures see plates at end of the paper. 
