THE SENSE OF SMELL IN BIRDS 641 
4. MORPHOLOGICAL RESULTS 
The anatomical studies made by the writer have given evidence 
that (1), the olfactory organs of birds are of too great size to be 
set aside as non-functional, but that (2) there is a tendency in the 
bird series towards retrogression of these organs. Various types 
of olfactory lobes and nerves have been figured in plates 1 and 2, 
and measurements for some of the birds studied have been given 
in table 1. 
In most of the orders, the olfactory lobes usually have essen- 
tially the form found in the doves and in the gallinaceous birds. 
They are so similar in the representatives of these two groups 
which were studied, that only one form has been chosen for illus- 
tration, and that is the species used by the writer in his experi- 
mental work (fig. 4). The so-called olfactory nerves usually 
leave the olfactory lobes in more or less close contact with each 
other, and they diverge gradually at some distance from their 
proximal ends as in fig. 4; but in some cases they are widely sep- 
arated (figs. 1, 8, 9, 18, 16, and 17). In table 1, some variations 
have been noted under the head of remarks. The length of the 
olfactory nerves and their degree of separation seem to be adapted 
to the form and arrangement of other structures in the head, and 
with no functional significance that could be discovered. Olfac- 
tory nerves, so called, were found in all of the material studied 
except for Dromaeus, Spheniscus, and Fulmarus. In these three 
birds, the olfactory lobes have their anterior ends in contact with 
the nasal capsules, though Dromaeus may possibly be said to 
have very short olfactory nerves. 
In no case was more than one pair of olfactory nerves found 
except possibly in Rhea. Unfortunately, the available material 
was not in a condition to give a satisfactory dissection for this 
species. 
The most interesting olfactory organs in some respects were 
those found in Dromaeus, Fulmarus, Catharistes, Cathartes, and 
the Corvidae. In Dromaeus and in Fulmarus, the olfactory lobes 
are notable for their relatively great size (figs. 2, 3, 5, and 6). 
It will also be observed that there is a constricted connection of 
