Report on the progress of human anatomy and physiology in the year 1844-5 / [Sir James Paget].

  • James Paget
Date:
1846
Catalogue details

Licence: Public Domain Mark

Credit: Report on the progress of human anatomy and physiology in the year 1844-5 / [Sir James Paget]. Source: Wellcome Collection.

    17/64 (page 17)
    But the absolute quantities of C02 exhaled in a minute in the same circum¬ stances are (since by rapid breathing the whole quantity of air that is breathed is proportionally increased) as follows: with 6 respirations per minute, 1/1 cubic inches; with 12, 246 cubic inches; with 24, 396 cubic inches; with 48, 696 cubic inches ; with 96, 1296 cubic inches. 2d. By increns ng the volume or depth of the respiration, the per centage proportion of C02 in the expired air is diminished; in the deepest respiration it is 1-97 per cent, less than in ordinary breathing. But for this proportionate diminution also there is a full compensation in the greater total volume of air which is thus breathed ; for equal volumes of expired air, whether breathed slowly or quickly, deeply or not,contain equal quantities of C02. 3d it appears, moreover, that if the air in one ordinary expiration contains on an average 4*48 per cent, of carbonic acid, the air expired in the first half of the whole expiration contains *76 per cent, less than this average, and that expired in the last half contains -96 per cent, more than the average, proving that the air in the parts of the lungs nearest the great bronchial tubes contains less COa than that in the deeper and more distant parts does.f 4th. In holding the breath, the proportion of C02 in the air within the lungs increases greatly, but in a diminishing ratio ; in one minute’s hold¬ ing it becomes 2*42 per cent., and in 100 seconds 3’0S per cent, more than it is in an ordinary expiration. In this condition also the composition of all the air within the lungs very soon becomes uniform. Finally, Vierordt shows how wide the range of occasional variation is within which, even in health and perfect bodily rest, the several parts of the respira¬ tory functions are discharged. In these conditions the pulse ranged, in occa¬ sional instances, between 54 and 101 per minute; the respirations between 9 and 15 ; the expired air between 1637 and 3676 cubic inches ; the carbonic- acid therein contained, between 3-358 and 6-22 per cent.; the volume of each expiration between 144-6 and 275 cubic inches The changes in the quantity of carbonic acid exhaled in much higher and lower temperatures than Vierordt observed them in have been investigated by M. Letellier.]; The experiments were performed on small birds, mice, and guinea pigs, who were made to respire for periods varying from half an hour to six hours. The results are stated in tables which show generally that the quan¬ tity of carbonic acid exhaled at a temperature between 82° and 104° was about as much below the average at ordinary temperatures as the quantity exhaled at temperatures about zero were above the same average; and the greatest quantity exhaled at the lower temperatures was about twice as much as the smallest exhaled at the higher temperatures. None of the animals experi¬ mented on could live without danger in a temperature equal to that which is natural to their own bodies; and all speedily died when the temperature was increased to 5° higher. At temperatures from 80° to 92° they lived and breathed quite tranquilly. Hannover,§ also, has instituted experiments to determine the quantities of carbonic acid exhaled in certain diseases, and finds, 1, that chlorotic females exhale an absolutely larger quantity of it than healthy ones do; 2, that the quantity is much diminished in all cases of phthisis; and, 3, that it is little or not at all changed in bronchitis. Asphyxia. Many interesting matters connected with the physiology of re¬ spiration are well discussed and illustrated by Mr. Erichsen,|| in his essay on * The author hence deduces a general rule for calculating the proportions, in which, however, he is probably premature. t See, on the anatomical adaptation of the lungs to this condition, Mr. Rainey’s Observations, at p. 14. j Annales de Chimie et de Physique, Avril 1845, p. 478. § De Quantitate . . . acidi eavbonici ab homine sano et tegroto exhalati; Havniae, 1845, 8vo. || An Experimental Inquiry into the Pathology and Treatmentof Asphyxia; Edinburgh, 1845,8vo.