Stru&ure and 0 economy of Whales. 431 
The external opening begins by a fmall hole, fcarcely percep- 
tible, fituated on the fide of the head a little behind the eye. It is 
much longer than in other animals, in confequence of the fizeof 
the head being fo much increafed beyond the cavity that contains 
the brain. It paffes in a ferpentine courfe, at fird horizontally, 
then downwards, and afterwards horizontally again, to the mem- 
brana tympani, where it terminates. In its whole length it is com- 
pofed of different cartilages, which are irregular and united toge- 
ther by cellular membrane, fo as to admit of motion, and probably 
of lengthening or (hortening, as the animal is more or lefs fat. 
The bony part of the organ is not fo much inclofed in the 
bones of the Ikull as in the quadruped, confiding commonly 
of a didinft bone or bones, clofely attached to the ikull, but 
in general readily to be feparated from it ; yet in fome it fends 
off, from the pofferior part, proceiles which unite with the ikull. 
It varies in its ihape, and is compofed of the immediate organ 
and the tympanum. 
The immediate organ is, in point of fituation to that of the 
tympanum, fuperior and internal, as in the quadruped. The 
tympanum is open at the anterior end, where the Euffachian • 
tube begins. 
The Euffachian tube opens on the outfide of the upper part 
of the fauces: in fome higher in the noie than others; 
higheft, I believe, in the Porpoife. From the cavity of the 
tympanum, where it is rather larged, it pafles fonvards and 
inwards, and near its termination appears very much fafcicu- 
lated, as if glandular. 
The Eudachian tube and tympanum communicate with feve- 
ral finufes, which pading in various diredfions furround the 
bone of the ear. Some of thefe are cellular, dmilar to the 
cells of the madoid procels in the human fubjeff, although 
not bony. There is a portion of this cellular druclure ot a 
Vol. LXXVII. P P p parti- 
