lO PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
Boulart^ in the Orang. In former descriptions it has been assumed that 
these sacs are found only in the older animals; the great development of 
them in my young specimen disproves this statement. It would seem 
that they are seldom developed symmetrically, but one sac is always 
larger than the other. This disparity in size may be great; thus Deniker 
and Boulart found in one Orang the left sac measured ii cm. long, 
whilst the right sac in the same animal was only 41 mm. The larger 
sac also often overlaps the smaller, and may completely conceal it lying 
in the middle line of the neck ; this probably accounts for the circum- 
stance that some anatomists have been led to describe the sac as a 
single azygos structure. Careful search in cases where the sac 
appeared single has led to the discovery that both sacs were present, 
one being of very diminutive proportions. Huxley‘S describes the great 
development of these sacs in a Gorilla in the following terms : — “ The 
larynx in its general characters resembles that of man and the Chimpan- 
zee ; connected with it in the adult Gorilla is a system of great cavities, 
developments of the two laryngeal sacculi, each of which is equally 
dilated, and produced into large caecal sacculated pouches, extending 
all over the sides of the neck in the interspaces between the muscles? 
from the rami of the lower jaw to the axillae. As age advances the sacs 
of the tvvo sides coalesce in the middle line over the trachea, and form 
an elongated bag, the upper end of which fits into the hollow of the body 
of the hyoid bone. The use of this immense and complex apparatus ” 
Prof. Huxley adds “ is not known.” 
The most extensive development of the laryngeal pouches is found in 
Duvernoy’s description of the Gorilla.^ In an adult male Gorilla a large 
median portion situated in the middle line of the neck was found, from 
which three pairs of lateral prolongations passed. Two superior ones, 
one on either side, passed upwards behind the angle of the lower jaw, 
passing back beneath the sterno-hyoid, the omo-hyoid and the sterno- 
mastoid muscles ; these superior branches of the median sac had the 
most direct communication with the ventricles of the larynx into which 
they opened, immediately between the hyoid bone and the thyroid cartil- 
age. These two superior branches also communicated each by a large 
aperture with the great median sac which descended anteriorly over the 
thorax and gave off a second and a third pair of lateral branches, with 
each of which its cavity freely communicated. The second pair (median) 
1 Deniker and Boulart. “ Les Sacs Laryng-iens des Singes anthropoides,” Journal de 1 ’ Anatomic et de 
la Physiologic, Paris, 1886, p. 51. 
2 Loc, cit., Vol. I, p. 538. 
3 M. Duvernoy, “ Des caracteres anatomiques des grands singes pseudo-anthroponiorphes,” Archives 
du Museum d’Histoire Naturelle, Paris, 1855-56, pp. 201, 202, 203. 
