150 COMPARATIVE ANATOMY AND PATHOLOGY. 
some complexity of organization. In the turkey there is no trace of a 
ganglion, but the nerve proceeds as a small round cord from the ante- 
rior apex of each hemisphere ; and, in the latter, it is not more than 
one-fifth part of the size of that in the former. The division of 
the supra-orbital branch of the fifth pair, which ascends from the 
orbit, and passes into the nose to the olfactory nerve, is about the 
same size in both. 
In all graminivorous birds these nerves are exceedingly small ; 
and, as their natural food has but little odour, we find that they are 
easily deceived by almost any thing which bears a resemblance to 
it. I will give you a little task in comparative anatomy. The 
subjects you will probably have in your own poultry yard. Dis- 
sect the head of a fowl and duck, or a turkey and a goose, for the 
sake of observing the different structure and size of these nerves, 
— I will speak by and by of their distribution. The fowl and the 
turkey have little more to do than to pick up the grain which is 
thrown to them — their scent is rarely or never put to the test ; but 
the duck and the goose are dabbling all day long in the pools or 
ditches for some additional food, and they have occasion for an acute 
sense of smell in order to distinguish the nutritive particles from 
those that are deleterious. The olfactory nerve, beside its complex 
origin, is full five times as large in the duck and the goose as in 
the fowl and the turkey. These, and many others of the same 
kind, are little anatomical exercises that will do you no harm. 
Fishes . — Dare I consider these as our patients 1 I do, and our 
legitimate ones too. They are destined for food — they are artifi- 
cially treated in our ponds and stews, and they are subject to dis- 
ease. I have been three times consulted with respect to them, 
and, in one case, my advice obtained for me a kind and powerful 
friend. 
All fish are carnivorous, and they are exceedingly voracious. 
The element which they inhabit, and the nature of their prey, 
render great acuteness of smell essential to their very existence. 
The recollections of the fisherman will sufficiently prove that this 
sense is exceedingly acute in these animals. In punt-fishing, who 
ever had much sport in the neighbourhood of a brother angler 
who was provided with carrion-gentles 1 Here, again, will be an 
interesting coincidence between the wants of the animal and the 
provisions which are made for their supply. The olfactory nerves 
have in them all a complex origin. They arise from the rudimen- 
tary hemispheres of the brain, as Dr. Grant very properly terms 
them ; and they rapidly swell into tubercles, varying in number and 
in size, and, in some fish, more than doubling the brain in bulk, and 
which have by certain anatomists been mistaken for the brain. I 
will, however, say no more of them, than that this varying bulk 
