ACTION OF THE ATMOSPHEKIC PRESSURE. 203 



They often undergo fatty degeneration, and they may contain pigment-granules (3) ; or they 

 may present the appearance of what Buhl has called "myelin degenerated cells," i.e., cells filled 

 with clear refractive drops of various sizes, some colourless, others with coloured particles, the latter 

 having been absorbed (4). Mucin in the form of myelin drops (5) is always present in sputum. 



2. Lymphoid cells (9) are colourless blood-corpuscles which have wandered out 

 of the blood-vessels ; they are most numerous in yellow sputum, and less numerous 

 in the clear mucus-like excretion. The lymph-cells often present alterations in their 

 characters ; they may be shrivelled up, fatty, or present a granular appearance. 



The fluid substance of the sputum contains much mucus, arising from the 

 mucous glands and goblet cells, together with nuclein, and lecithin, and the con- 

 stituents of saliva, according to the amount of the latter mixed with the secretion. 

 Albumin occurs only during the inflammation of the respiratory passages, and its 

 amount increases with the degree of inflammation. Urea has been found in cases 

 of nephritis. 



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 luug ; 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 

 most of the other elements, leaving the elastic fibres untouched.] Their presence 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 in bundles of fine needles (fig. 149, a). They 

 indicate great decomposition of the stagnant secretion. Leucin and tyrosin crystals are rare 

 ( 269). Tyrosin occurs in considerable amount when an old abscess breaks into the lungs. 

 Colourless, sharp-pointed, octagonal or rhombic plates Charcot's crystals (c) have been found 

 in the expectoration in asthma, and exudative affections of the bronchi. Hsematoidin (b) and 

 cholesterin crystals (d) occur much more rarely. 



Fungi and other lowly organisms are taken in during inspiration ( 136). The threads of 

 Leptothrix buccalis (12), detached from the teeth, are frequently found. ( 147). Mycelium and 

 spores are found in thrush (Oidium albicans), especially in the mouths of sucking infants. In 

 malodorous -expectoration rod-shaped bacteria are present. In pulmonary gangrene are found 

 monads, and cercomonads ; in pulmonary phthisis the tubercle bacillus ; very rarely sarcina, 

 which, however, is often found in gastric catarrh in the stomach and also in the urine ( 270). 



Physical Characters. Sputum, with reference to its physical characters, is described as 

 mucous, muco-purulent, or purulent. 



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 disagreeable 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. This pressure acts equally on all sides upon the 

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

 stantly filled with air (the respiratory passages and the spaces in the superior maxil- 

 lary, frontal, and ethmoid bones), and those that are temporarily in direct communi- 

 cation with the outer air (the digestive tract and tympanum). As the fluids of the 

 body (blood, lymph, secretions, parenchymatous juices) are practically incompres- 

 sible, their volume remains unchanged under the pressure ; but they absorb gases 

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

 the individual gases), and according to their temperature ( 33). The solids 

 consist of elementary parts (cells and fibres), each of which presents only a micro- 

 scopic surface to the pressure, so that for each cell the prevailing pressure 

 of the air can only be calculated at a few millimetres a pressure under 

 which the most delicate histological tissues undergo development. As an example 



