PNEUMATIC GUN 



PNEUMONIA 



253 



even in comparatively large, industrial establish- 

 ments is now in successful operation in Paris. A 

 complete plant to supply air pressure was first put 

 down there in 1870 in connection with a pneumatic 

 clock system, and about 8000 of these clocks are 

 now kept in motion by this means. But the 

 demand for compressed air for other purposes 

 increased rapidly, so that for some years past 

 only a comparatively small proportion of what 

 is supplied by the Paris company is required for 

 clocks. This company has compressing engines, 

 worked by steam, which have an aggregate of 

 3000 horse-power. These transmit air at a pressure 

 of from 80 to 90 Ib. per square inch through 30 

 mill's of mains. The air in the branch pipes has 

 its pressure somewhat reduced by passing it 

 through a regulator before being conducted to a 

 motor, which obviates any inequality that might 

 otherwise arise in the pressure if the air were 

 admitted direct to the motor at what it stands 

 in the mains. The amount of compressed air 

 used by any individual or firm is measured by 

 a meter. In 1889 works were established on a 

 large scale in Birmingham to supply compressed 

 air to that town by a system similar to that 

 adopted at Paris. In both of these towns 

 there is a large number of small workshops or 

 industrial establishments where power supplied in 

 this way can be used to drive small machines more 

 economically than by any other method. Other 

 applications of it are to raise water to the upper 

 stories of a building from a well in the basement, 

 for refrigeration, and for winding up telegraphic 

 instruments. 



Pneumatic dun. See AIR-GUN, CANNON. 



Pneumatics is a name, not very much used 

 now, for the science that discusses the properties of 

 gaseous fluids. It is therefore a branch of Hydro- 

 dynamics (q.v.), in the modern acceptance of that 

 term. See also ATMOSPHERE, BAROMETER, GAS, 

 SOUND, VISCOSITY, WAVE, WIND. 



Pneumatic Trough is a piece of chemical 

 apparatus devised by Priestley, by means of which 

 gases can be collected in vessels for experiments or 

 examination. It consists of a vessel of water, pro- 

 vided with a ledge or shelf at the depth of two or 

 three inches from the top. The jars in which the 

 gas is to be collected are filled with water, and 

 placed with their mouths downward upon the shelf, 

 which is kept a little under water, so as to prevent 

 the entrance of air into the jars. When the edge 

 of the jar is brought over the extremity of the tube 

 carrying the gas the bubbles of gas rise through 

 the water, collect in the upper part of the jar, and 

 displace the liquid. 



Pneumogastric Nerve. See NERVOUS 

 SYSTEM, VoL VII. p. 441, and DIGESTION ; also 

 Habershon, Pathology of the Pneumogastric Nerve 

 <2d ed. 1885). 



Pneumonia, or Inflammation of the Lungs, is 

 the name applied ( with the necessary qualification ) 

 to a numl*er of distinct pathological conditions. 

 The catarrhal inflammation of Bronchitis (q.v.) 

 may extend to the alveoli of the lungs, producing 

 scattered patches of catarrhal pneumonia. The 

 inflammatory changes in the langs in consumption, 

 including interstitial pneumonia, or cirrhosis of 

 the lungs ; in a few cases of syphilis ; in wounds 

 and injuries of the chest ; in pyiemia ; in the last 

 stage of many exhausting diseases, all come under 

 this head. But the most important form, to which 

 the present discussion will be restricted, is that 

 variously called acute, idiojiathic, lobar, or croup- 

 <nu pneumonia, and is one of the most striking 

 and definite of familiar diseases. 



The changes occurring in an affected portion of 

 Jung nre described in three stages. ( I ) Congestion : 



the lung-tissue still contains air, though less than 

 in health, and is gorged with blood. (2) Red hepa- 

 tisation: the lung-tissue is solid like liver (hence 

 the name), and is much more friable than in health ; 

 it still contains much blood, but no air, as the 

 vesicles are completely filled with firm exudation, 

 consisting of fibrinous material, mixed with leu- 

 cocytes and red blood-corpuscles. (3) Gray hepa- 

 tisation: the tissue is still more friable and of a 

 grayish colour, containing now little blood or blood 

 pigment ; the exudation has become much softer, 

 as the fibrinous material has disappeared, and it 

 oozes in part from the cut surface as a purulent 

 fluid. It is doubtful whether recovery can take 

 place when this third stage has been reached. 

 When the surface of the lung is affected Pleurisy 

 (q.v.) is always present as well as pneumonia. 



The inflammation never attacks the whole of 

 both lungs at once ; the right is more often affected 

 than the left, and the lower part than the upper. 

 A whole lobe, or a large part of it, usually sutlers ; 

 sometimes more than one. 



The disease generally begins suddenly with a 

 severe rigor or sliivering-fit, and the temperature 

 rises rapidly usually to 103-105 F. The pulse 

 and respirations are both quickened, but the latter 

 much more in proportion than in most other 

 diseases, a most important indication of the nature 

 of the case : instead of the usual ratio (about 4 

 pulse-beats to 1 respiration), the proportion be- 

 comes 3 or 2 to 1. All the usual signs of fever are 

 present ; but the patient's face presents a charac- 

 teristic dusky flush ; there is frequently severe 

 pain in the affected part of the chest, and usually 

 more or less cough, painful, but short, and sup- 

 pressed as far as possible. In most cases after a 

 tew days the spit becomes very viscid and tena- 

 cious, and assumes a rusty tinge ; this appearance is 

 almost sufficient by itself to show the nature of the 

 disease; but spit as well as cough may he absent 

 altogether. The physical signs of the disease are 

 very distinct. There is dullness on percussion over 

 the affected area ; and on auscultation marked and 

 very characteristic changes in the breath-sounds. 

 But if the inflammatory process happen not to 

 reach a portion of the lung in contact with the 

 chest- wall it may be impossible to detect anything 

 abnormal. 



It is always a serious disease ; but the great 

 majority of cases do recover. The circumstances 

 which make it most alarming are the presence of 

 other disease, especially of the heart or kidneys ; 

 previous habits of intemperance ; and advanced 

 age, as it is much leas fatal in youth and middle 

 life than after the age of sixty. Yet sometimes 

 even cases apparently far from hopeful ultimately 

 do well. 



In favourable cases the fever usually terminates 

 very rapidly, by crisis, as it is termed ; in a few 

 hours the temperature falls five or seven degrees, 

 and the patient's discomfort becomes correspond- 

 ingly relieved. In a very large proportion of cases 

 this takes place between the sixth and the eighth 

 day ; but it may occur earlier, or it may be delayed 

 to the fourteenth. After this has taken place the 

 exudation in the affected portion of lung is gradu- 

 ally expectorated and absorbed, and as a rule 

 perfect recovery takes place. 



In a considerable number of cases pneumonia 

 seems to be brought on by exposure to cold or wet. 

 But in the majority no such cause can be traced. 

 Only in very exceptional instances does it seem to 

 be infectious ; but epidemics on a small scale are 

 of not infrequent occurrence, and sometimes assume 

 large proportions. These facts, among others, have 

 led many observers to believe that acute pneumonia 

 ought really to be classed not with local inflam- 

 mations, but with specific fevers ; and that 1 1m 



