RESPIRATION OF FOREIGN GASES. 245 



It is remarkable that frogs, when placed in air free from oxygen, will for 

 several hours give off just as much carbon dioxid as in air containing oxygen, 

 and this without any obvious disturbances. Hence, the formation of carbon dioxid 

 must be independent of the absorption of oxygen, and the carbon dioxid must be 

 set free in the decomposition of other compounds. Finally, however, complete 

 motor paralysis sets in, while the circulation for a time remains undisturbed. 



RESPIRATION OF FOREIGN GASES. 



No gas is able to support life without a sufficient admixture of oxygen. Hence, 

 without oxygen, all other gases will quickly cause suffocation (in two or three 

 minutes) , even though they be in themselves harmless and indifferent. 



Completely indifferent gases are represented by nitrogen, hydrogen, and 

 marsh-gas (CH 4 ). The blood of an animal breathing any of these gases yields 

 no oxygen to it. 



Poisonous Gases. 



(a) Those displacing oxygen: (i) Carbon mpnoxid (CO). (2) Hydrocyanic acid 

 (CNH) displaces (?) oxygen from the hemoglobin, with which it forms a more stable 

 compound, and it thus kills with great rapidity. Further, it prevents the forma- 

 tion of ozone from the oxygen in the blood. Blood-corpuscles charged with hydro- 

 cyanic acid lose the property of decomposing hydrogen dioxid into water and 

 oxygen. 



(b) Narcotic gases: (i) Air containing o.i per cent, of carbon dioxid has been 

 designated as "bad air"; still, the discomfort experienced in such an atmosphere 

 (for example, in overcrowded rooms) arises rather from offensive exhalations of 

 unknown character than from the carbon dioxid itself. Air containing i per cent, 

 of carbon dioxid produces marked discomfort; with 10 per cent, life is endangered, 

 and with a higher percentage death ensues, accompanied by symptoms of coma. 

 (2) When nitrous oxid (N 2 O) is respired, mixed with one-fifth its volume of oxy- 

 gen, it causes in from one and one-half to two minutes a short, evanescent, especially 

 pleasurable state of intoxication (laughing-gas) , which is followed by an increased 

 excretion of carbon dioxid. (3) Pure ozonized air produces similar effects; it also 

 causes short, agreeable excitement, then drowsiness and rapidly transient sleep. 



(c} Reducing gases, (i) Hydrogen sulphid (H 2 S) rapidly deprives the erythro- 

 cytes of all oxygen, forming sulphur and water by oxidation; death occurs quickly, 

 even before the gas can effect any change in the hemoglobin, with the formation 

 of sulphur-methemoglobin. In addition, hydrogen sulphid forms in the blood 

 sodium sulphid from sodium carbonate, the new compound rapidly causing death. 



(2) Hydrogen phosphid, phosphin (PH 3 ), is oxidized in the blood to form 

 phosphoric acid and water, with decomposition of the hemoglobin. 



(3) Hydrogen arsenid, arsin (AsH s ), and hydrogen antimonid, stibin (SbH 8 ), 

 act like hydrogen phosphid, but in addition they allow the hemoglobin to pass 

 out of the stroma, so that the excreta, as the urine, contain hemoglobin. 



(4) Cyanogen (C 2 N 2 ) withdraws oxygen and further decomposes the blood. 

 Irrespirable gases cannot be inspired at all, as they cause reflex spasm of 



the glottis on entering the larynx. If introduced forcibly into the air-passages, 

 they give rise to violent inflammatory processes, followed by other disturbances 

 and death. Included in this class are hydrochloric acid (HC1) , hydrofluoric acid 

 (HF1), sulphurous acid (SO 2 ), nitrous acid (N 2 O 4 ), nitric acid (N,O 5 ). ammonia 

 (NH 3 ), chlorin, fluorin, iodin, bromin, undiluted ozone, and pure carbon dioxid. 



OTHER INJURIOUS SUBSTANCES IN THE INSPIRED AIR. 



Particles of dust are among the impurities of the atmosphere that are harmful 

 in large quantities and after long-continued action. Most of these particles are 

 expelled externally by means of the ciliated epithelium of the respiratory organs, 

 whose cilia wave toward the larynx. Some of the dust-particles, however, pene- 

 trate the epithelium of the air- vesicles, and thus reach the interstitial pulmonary 

 tissue, from which they frequently pass through the lymph- vessels to the lymphatic 

 glands of the lungs. For this reason coal-dust is found deposited in the lun, 

 of all elderly persons, blackening the alveoli. In moderate amounts 

 stances are harmless in the tissues; but if the deposits become large, they may 

 cause pulmonary diseases that may finally lead to disintegration of the lungs. 

 The particles penetrate between the alveolar epithelium into the i 

 monary tissue, and then into the lymphatic vessels and glands. In many trades 



