THE SENSE OF SMELL IN BIRDS 645 
argues for the greatest reduction of the sense of smell in this 
family. 
The olfactory lobes of the two parrot heads which were dis- 
sected were found to be so merged with the fore brain lobes as to 
be undefinable, (fig. 13). Apparently the organs of smell are not 
well developed in these birds. The representatives of the Passer- 
ine birds studied were all found to have extremely small olfactory 
lobes and nerves, as has been the observation of otherwriters. 
The condition shown in fig. 16, is characteristic for the finches. 
The writer agrees with Scarpa (’89), Schultze (’62), and Bumm 
(83) in finding olfactory organs of good size in the swimming 
birds. These organs are also fairly large in the shore birds 
(Charadriiformes). The olfactory lobes and nerves of the birds 
of prey have, on the other hand, been found to be of relatively 
moderate size, thus confirming Bumm’s observation. In fig. 12, 
a peculiarly fused and elongated condition of the olfactory lobes 
has been illustrated. In the specimens of the other birds of prey 
which were studied, these organs were more or less similar to 
those of the doves. 
On comparison of all the available material, the olfactory organs 
are found to be, in general, largest in the so called lower groups 
and progressively smaller in the higher orders. The sense of 
smell has evidently been disappearing in birds with the great 
development of the sense of vision. It seems not at all improba- 
ble that the sense of smell may be practically lost in the Passer- 
ine birds. 
The ophthalmic branches of the trigeminus after emerging from 
the orbits usually cross the olfactory nerves dorsally near their 
distal ends. Their course is often so close to that of the olfactory 
nerves at this place as to make it easy to confuse the trigeminus 
with the olfactory nerve. In the figures, the trigeminus nerve 
branches have been drawn slightly separated when desirable for 
the sake of clearness. In those forms where the trigeminus bran- 
ches to the upper mandible were found to be especially large, the 
olfactory lobes and nerves were also of good size as arule, and it 
seems not impossible that they may function in the feeding oper- 
ations of birds like the ducks, the flamingos, etc., in more or less 
intimate relationship with the trigeminus. 
