File:A text-book of physiology, for medical students and physicians (1907) (14591600559).jpg

Identifier: textbookofphysio1907howe (find matches)
Title: A text-book of physiology, for medical students and physicians
Year: 1907 (1900s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology Physiology
Publisher: Philadelphia, London, W.B. Saunders Co.
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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ar workeffects any change in the nature of the material consumed inthe body. Experiments made upon this point indicate thatthe R. Q. is not changed by muscular work when it is notexcessive or prolonged. Consequently we may infer that thesame kind of material, sugar, for example, is oxidized by thecontracting muscle as by the muscle at rest. In prolongedor fatiguing muscular work the R. Q. may be lowered, due 686 PHYSIOLOGY OF RESPIRATION. probably to the body using more of its fat; or in some conditionsit may be raised, owing to some insufficiency in the respiratoryand circulatory apparatus in furnishing an adequate supply ofoxygen. Under certain special conditions the respiratoryquotient may exceed unity or fall distinctly below 0.7. A riseto a value over unity may occur temporarily because of increasedventilation of the alveoli. Deeper and more rapid breathingwill drive out some of the C02 in the air of the lungs and thusincrease greatly the R. Q. As previously stated, this increase
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Pig. 273.—Record showing typical Cheyne-Stokes respiration (from a case of aortic andmitral insufficiency with arteriosclerosis). The time record gives seconds. has in itself no nutritional significance, but it is a factor thatmust be allowed for in such experiments. A more suggestiveincrease of the R. Q. is observed during convalescence. In thisperiod, as is well known, an individual may increase in weightrapidly, chiefly from the laying on of fat. This fat is made inlarge part probably from the carbohydrate of the food. Anoxygen-rich food, therefore, is converted to an oxygen-poor one,so that some of the oxygen must be split off partly as carbondioxid, and there is a larger output of this substance in theexpired air. Modified Respiratory Movements. Laughing, coughing, yawn-ing, sneezing, sobbing, and even vomiting may be considereda.- mollified respiratory movements, since the same group of musclescome into play. These are all movements, with the exception ofyawning, which may be

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