ON THE ANATOMY OF THE NORTHERN BELUGA. 401 
that of the fourth and fifth stomachs, and differing from that of the first and 
second. 
The interior of the fourth stomach corresponds exactly in form to that of 
its exterior. On its left wall, two inches from its posterior extremity, is the 
opening above described, by means of which this compartment communicates 
with that on its left. The opening into the fifth stomach is circular in form, 
and measures about half an inch in diameter. It is placed in the anterior wall 
of the cavity. The mucous lining is soft, uniformly smooth, and destitute of 
ruge. 
The cavity of the 7/th stomach commences by a blind extremity or cul-de- 
sac, on the posterior wall of which, and two inches from its deepest part, is 
placed the opening by means of which the fourth communicates with the fifth 
stomach. The duodenal extremity of the latter is narrower than any other 
part, and is furnished with a well-marked ring-like pyloric valve, in the centre of 
which is a circular opening one-fourth of an inch in diameter. The diameter of 
this compartment diminishes gradually from its commencement to its termina- 
tion, the latter being marked externally by a slight constriction. Its lining mem- 
brane resembles that of the fourth stomach, being smooth and devoid of ruge. 
None of the openings between the different gastric compartments presents the 
slightest trace of a valve. PrrrRIN* describes the canal-like communication 
between the second and third stomachs of Balwnoptera rostrata as beng 
provided with a valve at each extremity. 
From what has been said, it will be seen that in respect of the number of 
- gastric cavities in Beluga, our observations agree with those of Professor 
Wymay,t and differ from those of Barctay.t The latter author describes and 
figures only four compartments in this species, and an examination of the draw- 
ing which he appends to his description shows conclusively that he failed to 
recognise the third compartment above described. This is less to be wondered 
at, seeing that the cavity referred to is not distinguishable externally from the 
second and fourth, between which it hes. Dr BArctay, however, describes 
correctly the character of the mucous membrane of such compartments as he 
examined. 
An exact comparison of the stomach of Beluga with that of other cetaceans 
_ is, in the present state of our knowledge, well-nigh impossible, by reason of the 
diversity of statement which obtains with regard to the number of compart- 
ments in one and the same species according to different authors. In proof of 
this, we have thought it right to append the following tabular view of the 
_ observations of various anatomists who have examined the stomach of one or 
more species of cetacea :— 
*SVIL.p. 805. Ted ap. 607. { VIIL p. 382. 
VOL. XXIX. PART I. 5 L 
