524 COMPARATIVE AND HISTORICAL. 



Birds have an upper (larynx) and a lower larynx (syrinx) ; the latter is placed at the 

 bifurcation of the trachea, and is the true vocal organ. Two folds of mucous membrane (three 

 in singing birds) project into each bronchus, and are rendered tense by muscles, and are thus 

 adapted to serve for the production of voice. 



Amongst reptiles, the tortoises produce merely a sniffing sound, which in the Emys has a 

 peculiar piping character. The blind snakes are voiceless, the chameleon and the lizards have 

 a very feeble voice ; the cayman and crocodile emit a feeble roaring sound, which is lost in 

 some adults owing to changes in the larynx. The snakes have no special vocal organs, but by 

 forcing out air from their capacious lung, they make a peculiar hissing sound, which in somo 

 species is loud. Amongst amphibians, the frog has a larynx provided with muscles. The 

 sound emitted without any muscular action is a deep intermittent tone, while more forcible 

 expiration, with contraction of the laryngeal constrictors, causes a clearer continuous sound. 

 The male, in Rana esculenta, has at each side of the angle of the mouth a sound-bag, which 

 can be inflated with air and acts as a resonance chamber. The "croaking" of the male frog is 

 quite characteristic. In Pipa, the larynx is provided with two cartilaginous rods, which are 

 thrown into vibration by the blast of air, and act like vibrating rods or the limbs of a tuning- 

 fork. Some fishes emit sounds, either by rubbing together the upper and lower pharyngeal 

 bones, or by the expulsion of air from the swimming bladder, mouth, or anus. 



Some insects cause sounds partly by forcing the expired air through their stigmata provided 

 with muscular reeds, which are thus thrown into vibration (bees and many diptera). The 

 wings, owing to the rapid contraction of their muscles, may also cause sounds (flies, cockroach, 

 bees). The Sphinx atropos (death-head moth) forces air from its sucking stomach. In others, 

 sounds are produced by rubbing their legs on the wing-cases (Acridium), or the wing-cases on 

 each other (Gryllus, locust), or on the thorax (Cerambyx), on the leg (Geotrupes), on the abdomen 

 or the margin of the wing (Nekrophorus). In Cicadacia 1 , membranes are pulled upon by 

 muscles, and are thus caused to vibrate. Friction sounds are produced between the cephalo- 

 thorax and the abdomen in some spiders (Theridium), and in some crabs (Palinurus). Some 

 mollusca (Pecten) emit a sound on separating their shells. 



Historical. The Hippocratic School was aware of the fact that division of the trachea 

 abolished the voice, and that the epiglottis prevented the entrance of food into the larynx. 

 Aristotle made numerous observations on the voice of animals. The true cause of the voice 

 escaped him as well as Galen. Galen observed complete loss of voice after double pneumo- 

 thorax, after section of the intercostal muscles or their nerves, as well as after destruction of 

 part of the spinal cord, even although the diaphragm still contracted. He gave the cartilages 

 of the larynx the names that still distinguish them ; he knew some of the laryngeal muscles, 

 and asserted that voice was produced only when the glottis was narrowed. He compared the 

 larynx to a flute. The weakening of the voice, in feeble conditions, especially after loss of 

 blood, was known to the ancients. Dodart (1700) was the first to explain voice as due to the 

 vibration of the vocal cords by the air passing between them. 



The production of vocal sounds attracted much attention amongst the ancient Asiatics and 

 Arabians less amongst the Greeks. Pietro Ponce (t 1584) was the first to advocate instruction 

 in the art of speaking in cases of dumbness. Bacon (1638) studied the shape of the mouth for 

 the pronunciation of the various sounds. Kratzenstein (1781) made an artificial apparatus for 

 the production of vowel sounds, by placing resonators of various forms over vibrating reeds. 

 Von Kempelen (1769 to 1791) constructed the first speaking-machine. Rob. Willis (1828) 

 found that an elastic vibrating spring gives the vowels in the series U, 0, A, E, I according 

 to the depth or height of its tone ; further, that by lengthening or shortening an artificial 

 resonator on an artificial vocal apparatus, the vowels may be obtained in the same series. The 

 newest and most important investigations on speech are by Wheatstone, v. Helmholtz, Donders, 

 Brucke, &c, and are mentioned in the context. Hensen succeeded in showing exactly the 

 pitch of vocal tone, thus : The tone is sung against a Kbnig's capsule with a gas flame. 

 Opposite the flame is placed a tuning-fork vibrating horizontally, and in front of one of its 

 limbs is a mirror, in which the image of the flame is reflected. When the vocal tone is of the 

 same number of vibrations as the tuning-fork, the flame in the mirror shows on*e elevation, if 

 double, i.e., the octave, 2, and with the double octave, 4 elevations. 



