ACTION OF THE ATMOSPHERIC PRESSURE. 275 



The fluid substance of the sputum contains much mucus arising from 

 the mucous glands and goblet cells ; together with nuclein, and lecithin, 

 and the constituents of saliva according to the amount of the latter 

 mixed with the secretion. Albumin occurs only during inflammation of 

 the respiratory passages, and its amount increases with the degree of 

 inflammation. Urea has been found in cases of nephritis. 



Pathological. In cases of catarrh, the sputum is at first usually sticky and 

 clear (sputa cruda), but later it becomes more firm and yellow (sputa cocta). 

 Under pathological conditions there may be found in the sputum (a.) Red blood- 

 corpuscles from rupture of a blood-vessel. (b.) Elastic-fibres (10) from disintegration 

 of the alveoli of the lung; usually the bundles are fine, curved, and the fibres 

 branched. [In certain cases it is well to add a solution of caustic potash, which 

 dissolves the other elements and leaves the elastic fibres untouched.] Their pre- 

 sence always indicates destruction of the lung-tissue, (c.) Colourless plugs of 

 fibrin (11), casts of the smaller or larger bronchi, occur in some cases of fibrinous 

 exudation into the finer air-passages, (d.) Crystals of various kinds Crystals of 

 fatty acids (Fig. 1 15, a) in bundles of fine needles. They indicate great decomposition 

 of the stagnant secretion colourless, sharp-pointed, octagonal, or rhombic plates 

 (c) (Charcofs crystals) of unknown nature (perhaps tyrosin), Hsematoidin (b) 

 and cholesterin crystals (d) occur much more rarely. (/. ) Fungi and other lower 

 organisms frequently occur. The threads of leptothrix buccalis (12) ; Oidium 

 albicans in the mouth of sucklings, rod-shaped bacilli and bacteria. In phthisis, 

 the tubercle-bacillus of Koch. 



Abnormal coloration of the sputum red from blood when the blood remains 

 long in the lung it undergoes a regular series of changes and tinges the sputum 

 dark red, bluish brown, brownish yellow, deep yellow, yellowish green, or grass 

 green. The sputum is sometimes yellow in jaundice. The sputum may be tinged 

 by what is inspired [as in the case of the "black-spit" of miners.] 



The odour of the sputum is more or less unpleasant. It becomes very disagree- 

 able when it has remained long in pathological lung cavities, and it is stinking in 

 gangrene of the lung. 



139. Action of the Atmospheric Pressure. 



At the normal pressure of the atmosphere (height of the barometer, 

 760 millimetres Hg.), pressure is exerted upon the entire surface of the 

 body =15,000 to 20,000 kilos., according to the extent of the superficial 

 area (Galileo). This pressure acts equally on all sides upon the body, 

 and occurs also in all internal cavities containing air, both those that are 

 constantly filled with air (the respiratory passages and the spaces in the 

 superior maxillary, frontal, and ethmoid bones), and those that are 

 temporarily in direct communication with the outer air (the digestive 

 tract and tympanum ). As the fluids of the body (blood, lymph, secre- 

 tions, parenchymatous juices) are practically incompressible, their volume 

 remains practically unchanged under the pressure ; but they will absorb 

 gases from the air corresponding to the prevailing pressure (i.e., the 

 partial pressure of the individual gases), and according to their tempera- 

 ture (compare 33). 



