is aa 
XI. On the Cetacean Larynx. 
By Professor D’Arcy W. THompson. 
Some years ago Professor Howxs* detected in the larynx of the Porpoise a division 
of the great so-called arytenoid cartilage into two imperfectly separate parts. He 
suggested that of these only the lower represented the true arytenoid of other 
mammals, and that the long upper horn was the equivalent of the Cartilage of 
WRISBERG or cuneiform cartilage of human anatomists. This observation has been 
confirmed by Professor CLELAND? in regard to Lagenorhynchus albirostris ; but in 
general it has not received the attention which it deserved ; and various authors, 
including Max Weper and Dusors, Beaurecarp and Bounarr, have since 
discussed the Cetacean larynx without referring to Howes’ paper or rediscovering 
for themselves the condition which it describes. 
Tt is plain that if only a part of the great Cetacean “arytenoid” be the true 
arytenoid, then into that part alone should pass the several arytenoid muscles. On 
investigating a series of Cetacean larynges to determine this point, I find it to be 
strictly the case. 
The larynges that I have examined as yet belong all to the Delphinoidea, to 
wit, to the genera Monodon, Beluga, Lagenorhynchus, Delphinus, and Globioce- 
phalus: but doubtless as regards the arytenoids the generalisation drawn for the 
Delphinoids applies to the Balzenoidea also. 
In the larynx of a foetal Globiocephalus melas (Figs. 1—6), 45 cm. long, the true 
arytenoids (A7r') are still completely separate from the arytenoid cornua, which will 
be henceforth referred to as the supra-arytenoids. The arytenoids exhibit a 
rounded or somewhat triangular posterior surface, a prominent external border, and 
an elongated triangular external surface: the whole arytenoid has the form of a 
three-sided pyramid, whose base is posterior, and whose lower surface runs for some 
distance parallel to the superior border of the cricoid. The two arytenoids are set 
far apart from one another upon the cricoid, near the angles of the posterior surface 
of the latter cartilage. 
The form of the other cartilages is sufficiently shown in the figures. The 
cricoid is thick and massive posteriorly : it bears just at the posterior and inferior 
angle on each side an articular facet for the posterior horn of the thyroid: its own 
lateral horns curve downwards and forwards, and end freely in front near the 
middle line. 
* Journ. of Anat. and Phys. Vol. XIV., p. 471. 1880. 
+ “TJ beg to verify the observation of Mr Howzs that the cartilages which together with the epiglottis 
are so remarkably elongated in porpoises are not arytenoids, but articulate with them, and may be regarded 
as Cartilages of Wrisserc.” Journ. of Anat. and Phys., Vol. XVIII, p. 333. 1884. 
