630 R. M. STRONG 
imate only, because it was impossible to select points for measur- 
ing with any precision. The olfactory nerve diameter was the 
most important of the measurements, and it could be determined 
with somewhat greater precision than the others. Nevertheless, 
the olfactory nerve cross section varies in form and size at differ- 
ent points, and a mean diameter for the median portion was con- 
sequently sought. The olfactory nerves in some species are flatter 
laterally than in others. Where they were very much flattened, 
lateral and dorso-ventral diameters were measured. 
Photographs varying from one-half diameter to nearly natural 
size were made of the dissections in dorsal view. The heads 
were arranged so that the olfactory nerves were approximately 
at right angles to the axis of the camera. Some of the dissec- 
tions were also photographed from the side to give a lateral view 
of the olfactory lobes and nerves. Prints enlarged two or three 
diameters were then made from the negatives of subjects which 
were selected for illustration in this paper. A magnification of 
three diameters was used only for a few small birds. Most of 
this work was done with the Edinger drawing apparatus. When 
this apparatus was properly adjusted for an exposure, and before 
a print holder was inserted, a sketch was made of the image pro- 
jected on drawing paper. This sketch gave the general outlines 
for the making of a drawing. References were made frequently 
to measurements and to the enlarged prints in the preparation 
of the drawings. Three methods were thus available for secur- 
ing accuracy in the drawing of the illustrations. Most of the 
brain mass has been included in order to show the relative size 
of the olfactory lobes. 
Heads of the birds in the following list were dissected and stud- 
ied: The classification used in Sharpe’s Catalogue, (’74) and 
Handlist, (’99) is employed here and the orders are given so that 
the taxonomic distribution of the forms studied may be seen at 
a glance. The Sharpe Catalogue nomenclature has been followed 
consistently because at present there is no other work so rep- 
resentative of the birds of the world. As many of the specimens 
in the Edinger collection bore other names, they also are men- 
tioned after the Sharpe Catalogue name in parentheses. 
