The organ of smell is more simple. This sense lies, or is supposed to lie, in the mucous membrane which lines the nostrils and the openings in connection. Particles are constantly escaping from odorous bodies; and, by being inhaled in respiration, they are thrown in contact with the mucous membrane. _A._ Before leaving the head, will you tell us something of the organs of voice? _I._ By placing your finger on the top of your windpipe, you will perceive a slight prominence. In males this is very large. This is the thorax. It is formed of four cartilages, two of which are connected with a third, by means of four chords, called vocal chords, from their performing an important part in producing the voice. Experiments have been made, which prove that a greater part of the larynx, except these chords, may be removed without destroying the voice. Magendie thus accounts for the production of the voice. He says, "The air, in passing from the lungs in expiration, is forced out of small cavities, as the air-cells and the minute branches of the windpipe, into a large canal; it is thence sent through a narrow passage, on each side of which is a vibratory chord, and it is by the action of the air on these chords, that the sonorous undulations are produced which are called voice." _E._ Do not the lips and tongue contribute essentially to speech? _I._ They do not. Hayward says he can bear witness to the fact that the articulation remains unimpaired after the tongue has been removed. The labials, _f_ and _v_, cannot be perfectly articulated without the action of the lips.--What subject shall we take next? _A._ A natural transition would be from the head to the heart, and, in connection, the circulation of the blood. _I._ Yes. I will give you an abstract of the ideas I gained in the study of Hayward's Physiology, and the reading of Dr. Paley's Theology. The heart, arteries, and veins are the agents of circulation. The heart is irregular and conical in its shape; and it is hollow and double. _A._ There is no channel of communication between these parts, is there? _I._ None; but each side has its separate office to perform. By the right, circulation is carried on in the lungs; and by the left through the rest of the body. I will mark a few passages in Paley, for you to read to us, Ann. They will do better than any descriptions of mine.