

MECHANICAL PHENOMENA OF RESPIRATION, 305 



immersed in a water receiver, and to which an india-rubber 

 tube is attached, one end of which is placed in the mouth of 

 the person experimented upon. The movements in the air- 

 receiver are recorded by means of a movable indicator and a 

 .graduated and fixed scale. The person first takes a deep 

 inspiration, and then breathes into the tube, and thus the 

 maximum volume of the air inhaled is obtained. After ex- 

 perimenting in this manner on about 2000 persons, Hutch- 

 inson lays it down as a law that the maximum volume of air 

 exhaled in the normal condition is in regular, if not mathe- 

 matical proportion to the stature. In an athletic native of 

 America, he found that the maximum volume of air exhaled 

 was 7 litres (although the man died of consumption a few 

 years after). We give (Fig. 80) a sketch of Schnepl's spi- 

 rometer; it is only Hutchinson's instrument modified. The 

 air, exhaled through the tube A, is received into the receiver 

 C, which serves as a gasometer. 1 



The numbers given above represent extraordinary cases; 

 in calm, ordinary respiration only one-half litre of air is intro- 

 duced at each inspiration, and given out at each expiration. 

 The latter may be called the figure of normal respiration. 



then by horizontal linos, the movements of the valve, that is, the 

 impressions which it receives, as well as the spring, from more or 

 less intense or prolonged currents of air. The exquisite sensibility 

 of this instrument, recording the slightest movements of the air, 

 such as the bursting of a bubble in a flask, enables us exactly to 

 determine the frequency of the respiratory movements, the relative 

 length of each, their intensity, and, especially, theiryorm. (Ber- 

 geon and Kastus, " Recherches sur la Physiologic Medicale de la 

 Respiration, a 1'Aide d'un nouvel Instrument, L'Anapnographe." 

 Paris, 1809.) These writers have here made a collection of dia- 

 grams of remarkable accuracy, exhibiting special features, accord- 

 ing to the age of the subject, the exaggerated exercise or morbid 

 condition of the lungs, etc. 



The spirometer, evidently, might be employed to ascertain the 

 diminution in the pulmonary capacity at the beginning of phthisis, 

 when physical signs (auscultation) leave the physician in doubt; but, 

 for this purpose, it must have been previously measured in health. 

 Any disease, such as emphysema, pleurisy, etc., which diminishes 

 the space occupied by the air, or diminishes the quantity of air in 

 circulation, produces the same effect as phthisis. Spirometry, 

 therefore, cannot be said to be of any great use in medical prac- 

 tice. 



1 Schnepf, " Capacite Vitale du Poumon, ses Rapports Physi- 

 ologiques et Pathologiques avec les Maladies de la Poitrine." 



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