384 THE SOLIDS. 



tory information, are Emphysema, Asthma, Pulmonary'Apo- 

 plexy, Pneumonia, and Tubercle. 



Emphysema. The essential pathological and microscopical 

 characters of Emphysema consist in an enlargement and rup- 

 ture of a greater or less number of air cells, whereby the 

 cavities of several distinct cells become thrown into one, with 

 sometimes tho, escape of air from the ruptured air cells into 

 the interlobular cellular tissue. When the air cells are sim- 

 ply dilated and ruptured, without any escape of air from 

 them, the Emphysema is lobular; when, on the contrary, the 

 air passes from the cells into the cellular tissue, which unites 

 the lobules to each other, the Emphysema is termed inter- 

 lobular. It cannot be doubted but that this condition of the 

 lungs interferes very greatly with the efficiency of these 

 organs ; the extent of surface over which the air and blood 

 are brought into contact being very considerably diminished. 



Asthma. The microscope has revealed the fact that the 

 smaller bronchial tubes and air cells are principally consti- 

 tuted of a form of elastic tissue, which, possessing marked 

 physical properties, is yet, to a certain extent, under the 

 control of the nervous system. It is then the irregular 

 action and contraction of this tissue, determined partly by 

 physical causes and partly by irregular and unequal impres- 

 sions arising from internal causes conveyed to this tissue by 

 the nerves, which occasion and account for the distressing 

 and peculiar symptoms of Asthma. 



Pulmonary Apoplexy. Pulmonary apoplexy is simply a 

 highly congested condition of the vessels, ^Yhich are prin- 

 cipally capillary, of the lungs. A congested vessel is of 

 greater diameter than an uncongested one, and, therefore, is 

 capable of containing, and really does contain, a far larger 

 quantity of blood than the vessel in its normal state. There 

 are many stages or degrees of congestion and of pulmonary 

 apoplexy : the congestion may be slight, may engage only 

 one lung or a portion of one ; the dilatation of the vessels 

 may be but trifling, and therefore the increased quantity of 

 blood conveyed by them will be but small ; or, on the other 

 hand, the congestion may be very great, both lungs may be 



