

EFFECTS OF ATMOSPHERIC PRESSURE. 253 



paragraph (3) . According to the observations made by Whimper on himself during 

 the ascent ot the highest peak in the Andes, the body can, to a certain extent 

 accustom itself with respect to these latter phenomena. At an elevation of from 

 7000 to 8000 meters loss of consciousness occurs at times; the aeronauts Croce- 

 bpmelli and Sivel lost their lives at a height of 8600 meters, where the rarefied 

 air contains only 72 per cent, of oxygen (the air-pressure being 241 mm of mer- 

 cury). In dogs a marked fall in the blood-pressure occurred first at 200 mm of 

 mercury, accompanied by a small, slow pulse. 



The inhabitants of high, mountainous regions are sometimes attacked by an 

 illness (mountain-sickness), which consists essentially of symptoms similar to those 

 described, especially anemia of the internal organs, and which is accompanied bv 

 a diminution in the amount of hemoglobin in the blood. Alexander von Hum- 

 boldt found remarkable roominess of the thorax in the inhabitants of the high 

 Andes. This phenomenon has been attributed to a diminution in the carbon 

 dioxid of the blood, which serves as a stimulant to the respiratory center At an 

 elevation of from 6000 to 8000 feet above the sea, water contains only about one- 

 third the amount of air absorbed; therefore fish cannot longer live in it. 



Animals can be subjected to a still greater rarefaction of the atmosphere under 

 the receiver of an air-pump. Under such conditions birds die when the air-pressure 

 is reduced to 120 mm. of mercury; mammals at 40 mm. of mercury. Frogs 

 endure repeated evacuation, and as a result they become much distended by 

 escaping gases and aqueous vapor; after the entrance of air, however, they col- 

 lapse completely. Hoppe-Seyler ascribes the cause of death in warm-blooded 

 animals to the development of gas in the blood, the bubbles obstructing the capil- 

 laries. Landois has often been able to confirm this phenomenon, and as far back 

 as 1879 he suggested that the development of gas-bubbles in the parenchymatous 

 juices, especially of the nervous system, might act injuriously through mechanical 

 laceration of the tissues. Sudden reduction of a previously high air-pressure may 

 act in a similar manner. The free gas that forms in the blood is almost pure 

 nitrogen. The presence of air in the arteries of the spinal cord produces anemic 

 paralysis, and later local destruction of the nerve-elements. Redi and Wepfer, in 

 1685, were the first to observe death from blowing air into the veins, as a result 

 of mechanical obstruction to the circulation. 



Local diminution of the air-pressure results in marked congestion and swelling 

 of the tissues in the affected part ; this is shown in the simplest manner by cupping. 

 Under the name of the ' ' cupping-boot ' ' Junod described an apparatus for the rare- 

 faction of air, made to include a whole extremity; this apparatus rendered possible 

 a reduction to one-third in the air-pressure surrounding the leg. By this means 

 from 2 to 3 kilos of blood may be aspirated into the leg, thus producing a temporary 

 withdrawal of blood from other parts of the body, without causing a permanent 

 loss of blood to the body. The energetic application is exceedingly painful, and 

 the after-effects persist for 48 hours. 



Marked increase of the atmospheric pressure is accompanied by phenomena that 

 may for the most part be explained as the reverse of those described in the dis- 

 cussion of diminution of the air-pressure. They have been observed many times, 

 partly in so-called pneumatic cabinets, in which, for therapeutic purposes, the 

 pressure is gradually increased to one and one-fifth, two and two-fifths atmos- 

 pheres and more; partly in closed reservoirs used in construction under water, 

 and out of which the water is forced by pumping air in. Under such conditions men 

 work at times even under a pressure of four and one-half atmospheres. The fol- 

 lowing phenomena are worthy of attention: (i) Pallor and dryness of the external 

 surfaces, collapse of the cutaneous veins, reduction in perspiration and the secretions 

 from mucous membranes, greater supply of blood to the abdominal organs. (2) 

 Pressing inward of the tympanic membrane (until the Eustachian tube allows the 

 compressed air in the tympanic cavity to escape, often with a noise) ; considerable 

 pain in the ears and even impairment of hearing. (3) A feeling of lightness and 

 freshness during respiration. The respirations become slower (from 2 to 4 in a 

 minute), inspiration is made easier and shortened, expiration is lengthened, and 

 the pause is distinct. The capacity of the lungs is increased, owing to freer move- 

 ment of the diaphragm, in consequence of diminution in the gases contained in 

 the intestine. G. v. Liebig has noted an increase in the absorption of oxygen; 

 Panum found that with the same volumes of air interchanged, the excretion of 

 carbon dioxid is increased; the venous blood appears to be reddened. (4) Diffi- 

 culty in speaking, a nasal metallic tone to the voice, inability to whistle. (5) In- 

 creased secretion of urine; on account of the more rapid oxidation in the body, 



