Normal inspiration is produced by a regular contraction of the diaphragm, and expiration is due to the elasticity of the tissue of the lungs. A spasmodic inspiration, during which a prolonged contracted spasm of the diaphragm takes place, produces stammering; such a convulsive contraction of the diaphragm can take place without attempting to speak, but any attempt to utter sounds during the spasm will result in stammering. At the end of the spasm, the air is then quickly expelled from the lungs. I have noticed stammering children that I have treated subject to frequent attacks of hiccough; in hiccough the expiration is quiet: an irritation of the nerves of the diaphragm brings about, with a violent inspiration, an attenuated convulsive contraction of the diaphragm, as in stammering. In stuttering which is characterized by the presence of some spasm, in all articulations, labial, lingual, dental and guttural, although respiration is irregular and the respiratory organs do not work well, the inability to form and join the sounds comes from other sources than a spasmodic contraction of the diaphragm. Stammering proper, when organic, might be called stammering of the diaphragm, and that distinction would be quite logical, as other organs wholly unconnected with speech show that peculiarity of being affected with stammering. The influence exercised on the voice and speech by the respiratory mechanism is so considerable that a variety of theories on respiration have been advanced and discussed by physicians and specialists, not only with reference to speech impediments but specially for singing, elocution, acting and public speaking, and also in reference to general health. Writers and professors advocating exclusively so-called diaphragmatic, or costal, or abdominal respiration, are incorrect and perfectly deceived. The diaphragm, the ribs, and the muscles of the abdomen must all do more or less their special work, in order to carry on a normal and healthy respiratory act. An eminent physician, Dr. Ed. Fournié of Paris, says: “He who respires exclusively by one or the other of these alone (diaphragm, ribs or abdomen) must be indeed a sick man.” Costal or side-breathing is due to the elevation and depression of the ribs simultaneously with the contraction of the diaphragm. Abdominal breathing, the method taught to singers, is performed by the pressure of the abdominal muscles upon the anterior and lateral walls of the abdomen, forcing up the diaphragm, and thus expiring almost completely the air in the lungs. Medical and scientific investigations concerning speech defects have been as considerable as it is contradictory. The observations of prominent doctors and specialists, some of them being afflicted themselves, have in the most argumentative thesis attributed stammering-stuttering to numerous and varied causes, the enumeration of which has a real historical and pathological interest: