PNEUMONIA. 339 



but, as far as opinion goes, it may be assumed that there are strong 

 authorities against the hereditary nature of the diseases which pro- 

 duce roaring. That it is often the result of ordinary inflamma- 

 tion, which in itself can scarcely be considered hereditary, is plain 

 enough ; and that it is also produced by mismanagement in tight 

 reining is also admitted, which latter kind can scarcely be supposed 

 to be handed down from sire tc sou; but that it is safer, when 

 practicable, to avoid parents with any disease whatever, is patent 

 to all 



PNEUMONIA AND CONGESTION OF THE LUNGS. 



The theoretical definition of pneumonia is that it con- 

 sists of inflammation of the parenchyma of the lungs, independently 

 both of the mucous lining to the air passages, and of the serous 

 covering of the whole mass. The mucous membrane ceases ab- 

 ruptly at the terminations of the bronchial subdivisions, and 

 consequently the air-cells are not lined with a continuation from 

 it. Hence there is an extensive cellulo-fibrous area, which may 

 be the subject of inflammation, without implicating the mucous 

 surface. Until within the last fifteen or twenty years, it was com- 

 monly supposed that the air-cells were all lined by mucous mem- 

 brane, and that the parenchyma was confined to an almost infini- 

 tesimally thin structure, tilling up its interstices; but the microscope 

 Las revealed the true structure of the lungs, and has shown that 

 there is a well-founded distinction between bronchitis and pneu- 

 monia, upon the ground of anatomy, as well as observation. Still, 

 it cannot be denied that the one seldom exists to any great extent, 

 or for any long period, without involving the adjacent tissue ; and 

 broncho-pneumonia, as well as pleuro-pneumonia, are as common 

 as the pure disease. 



Pneumonia, or peripneumony, must be examined, with a 

 view, first, to its intensity, whether acute or sub-acute; and 

 secondly, as to its effects, which may be of little consequence, or 

 they may be so serious as to completely destroy the subsequent 

 usefulness of the patient. It is not, therefore, alone necessary to 

 provide against death by the treatment adopted, but due care must 

 also be taken that the tissue of the lungs is not disorganized by a 

 deposition of lymph, or of matter, so as to lead, in the one case, to 

 a conaoUdation of the air-cells, and, in the other, to the formation 



