406 VITAL HEAT. 



posterior portions of the vocal bands increases in size, the capitula 

 Santorini are tilted more and more forward, and the epiglottis rises 

 until a note in the neighborhood of E, treble clef, first line, is 

 reached. The cartilaginous glottis is then closed. The glottic 

 chink becomes much narrower and linear in shape, the capitula 

 Santorini are tilted backward, and the epiglottis is depressed. 



" When the vocal bands are shortened in the change at the 

 lower break in the voice, it is mainly due to closure of the carti- 

 laginous portion of the glottis, the ligamentous portion not usually 

 being affected. If, therefore, the cartilaginous glottis is not closed, 

 there is usually no material change in the length of the vocal 

 bands. 



" As the voice ascends from the lower break, the vocal bands 

 increase in length and diminish in width, the posterior portion of 

 the glottic chink opens more and more, the capitula Santorini are 

 tilted forward, and the epiglottis rises until, in the neighborhood 

 of E, treble clef, fourth space, another change occurs. 



" The glottic chink is then reduced to a very narrow slit, in 

 some subjects extending the whole length of the glottis. In others, 

 closing in front, or behind, or both. Not only is the cartilaginous 

 glottis always closed, but the ligamentous glottis is, I believe, 

 invariably shortened. The arytenoid cartilages are tilted back- 

 ward and the epiglottis is depressed. As the voice ascends in the 

 head register the cavity of the larynx is reduced in size, the aryte- 

 noid cartilages are tilted forward and brought closer together, the 

 epiglottis is depressed, and the vocal bands decrease in length and 

 breadth. If the posterior part of the ligamentous portion of the 

 glottis is not closed in the lower, it is likely to be in the upper 

 notes of the head register." 



VITAL HEAT. 



The temperature of a lifeless object is approximately that of 

 the air which surrounds it ; the temperature of a living object is 

 independent of the temperature of the air, although it may be 

 modified by it. This difference is due to the fact that living things 

 produce heat within themselves ; this is called " vital heat." Many, 

 perhaps most, authorities speak of it as " animal heat," but, though 

 it is most striking in members of the animal kingdom, yet inas- 

 much as its production is not confined to animals, but also occurs 

 in plants, the writer prefers the term vital heat as indicating that 

 the phenomenon is peculiar to the living condition, irrespective of 

 the question whether it occurs in an animal or in a vegetable. 



Warm-blooded Animals. The term warm-blooded was ap- 

 plied to certain animals because their temperature was so high as 

 to make them warm to the touch, while others were spoken of as 

 cold-blooded because they were cold to the touch. Thus, man, with 



