302 THE POPULAR SCIENCE MONTHLY. 



witnessed with profound interest by physicians and physiologists. In 

 1860 he came to Paris, and astonished many of the members of our 

 learned societies. He exhibited not only the whole of his own larynx, 

 but also the interior of his trachea down to the bifurcation a sight 

 well calculated to cause astonishment when one sees it for the first 

 time. The vocal organ cannot be examined with the same facility in 

 all persons, and some practice is needed for experimenting successfully. 

 Dr. Mandl and Dr. Krishaber possess an extraordinary power of con- 

 trolling the various movements of the larynx. After repeated experi- 

 ments we now fully understand the functions of the vocal organs in 

 speaking and in singing. The studies of Helmholtz upon the forma- 

 tion of sounds have thrown new light upon the phenomena of voice. 



The notes of an organ, when heard beneath the arched roof of a 

 cathedral, produce a profound impression. Inasmuch as no other kind 

 of music so closely resembles the human voice, we can fancy ourselves 

 communing with the thoughts and feelings of the human soul. We 

 naturally compare the organ to man's vocal apparatus. The organ 

 has a bellows, we have lungs ; in the organ is a " sound-board," the 

 trachea performs the same function ; the vibrating tongue of the or- 

 gan has its counterpart in our vocal cords ; and the pharynx and the 

 mouth answer to the resonating cavities of the organ. Yet the natu- 

 ral instrument is immensely superior to the artificial one. In the or- 

 gan there must be a number of pipes to produce the different sounds ; 

 in the natural instrument there is only one pipe for both speech and 

 song, but it is a wonderful pipe, being susceptible of endless modifica- 

 tions. It has a double vibrating spring and a resonator. The glottis 

 is the vibrating spring or tongue, and, according as the air-passage is 

 more or less narrowed, and the vocal cords more or less tense and 

 vibrant, the sounds emitted are either grave or sharp. The mouth 

 forms the resonator ; the cavity of the mouth is susceptible of almost 

 endless modifications, producing an infinite diversity of sounds. 



Our various senses are each affected by a special order of impres- 

 sions ; the organ of hearing takes note of sounds, which are propa- 

 gated by concussions of the air, by vibrations. When these vibra- 

 tions are continuous, regular, isochronous, they constitute a musical 

 sound ; when irregular, the result is noise. Sounds possess very defi- 

 nite characters, as intensity, pitch, timbre. Intensity depends upon 

 the amplitude of the vibrations, which travel in the form of concen- 

 tric spheres from the starting-point, as the waves caused by a peb- 

 ble dropped into water are diffused in the form of concentric circles. 

 Amplitude is always the result of the force of the primary shock. 

 The pitch of a sound is determined by the number of vibrations 

 occurring in the space of one second: when the vibrations are few, 

 the sound is grave ; when very numerous, it is sharp. In a word, 

 the shorter the duration of each vibration, the higher the pitch of 

 the sound. Timbre means quality of voice. We distinguish voices 



