At the back of our tongues, and also of those of the Gorilla, is a little flap, rather hard and gristly in us, and only membranous and soft in the Ape, which covers over the top of the air-passage into the windpipe when any food is swallowed. The food or drink would otherwise get into the air-passage, and would be constantly going “the wrong way.” Immediately under this flap, or, as it is called, the epiglottis, is a space limited in front by the hard substance we call in our throat the “Adam’s apple,” and at the bottom of it are the movable structures by whose action voice is produced. Now, in the this space is not shut in front as it is in us, but there are two openings in it, one on either side, which lead to a complicated sac or pouch. This pouch is made of thin membrane, and covers, when blown out like a bag--for the air coming out of the windpipe can be forced in--the front of the windpipe, and projects sideways under the muscles of the throat, and even amidst those of the armpits. The Gorilla can thus blow his neck out, as it were, and when he is yelling, the air in the bag or pouch must resound. Possibly this great bag of air may have something to do with making the body lighter when the animal is climbing and using all the force it can with its arms. These so-called “laryngeal” pouches are found in many Apes and Monkeys, but their double opening into the space below the little flap is peculiar to the great Apes, which are sufficiently man-like as to be called by the term Anthropoid--the Gorillas, their allies the Chimpanzees, the Orangs, and the Siamangs.[6] All the other Monkeys of the Old World with sacs have but one opening into a space, or, as it is termed, the ventricle of the organ of voice, or larynx. The Monkeys of the New World have a different arrangement of air pouches, which will be noticed in the proper place. The Gorilla has one little peculiarity which distinguishes it from all other Apes and Monkeys, and which causes it to be more like man, and insignificant as it may seem, it is of some interest. In man there is a decided projection of bone behind, or rather below the ear, and this is called the teat-shaped process of the ear-bone (Mastoid process), and is of importance to the organ of hearing and also to the muscles which steady and keep the head erect, and allow of its being moved in particular directions. This process exists to a certain extent in the Gorilla but not in the Chimpanzee, Orang-Utan, or in any other of the Quadrumana. It is smaller in the Gorilla than in man, but it is made up, as in us, of a number of spaces enclosed by bones which have to do with the organ of hearing in some way or other, and which are lined with membrane. On the outside a muscle is attached, which passes downwards and inwards to the top of the breast-bone, covering the great blood-vessels and nerves of the neck.