216 DISEASES OF THE PARENCHYMA OF THE LUNG. 



generated in the vesicles, the cells are more and more crowded to- 

 gether, thus becoming mutually injurious, and undergoing degen 

 eration. 



The knowledge that the majority of cases of consumption are not 

 the result of neoplasm but of inflammation, and that, when tubercles 

 exist in phthisical lungs, the tuberculosis is almost always preceded by 

 a pneumonic process, which, by caseous degeneration of its products, 

 has prepared the soil for the growth of tubercle, has been of material 

 assistance in explaining the etiology of consumption. Numerous 

 well-established facts, which had hitherto defied all interpretation (as 

 long as consumption was always ascribed to neoplasm), are now fully 

 reconcilable to the generally acknowledged laws of pathology. 



Predisposition to pulmonary consumption or, to speak more pre- 

 cisely, the predisposition toward pneumonia terminating in cheesy in- 

 filtration, is strongest in persons of feeble and delicate constitution. 

 It is by no means meant by this that vigorous persons, possessing 

 normal resisting power against noxious influences, enjoy an immunity 

 from this disease. Indeed, although it is somewhat rare, even croup- 

 ous pneumonia sometimes terminates in caseous infiltration, with sub- 

 sequent disintegration of the lung, in individuals who, prior to the 

 attack, were in perfect health, and gave no signs whatever of weakness 

 or delicacy of constitution. In a similar manner the most vigorous 

 and blooming children may be attacked by acute catarrhal pneumonia, 

 during the measles or whooping-cough, and may soon perish through 

 caseous metamorphosis of the pneumonic product. The origin of the 

 many deaths which have been observed to take place after an epi- 

 demic of measles or of whooping-cough, and which, until recently, has 

 been chiefly ascribed to tuberculosis, is, in most cases, really traceable 

 to the effect of a catarrhal pneumonia contracted during the course of 

 the above-named disorders. 



But even a simple, genuine catarrh may extend into the air-vesicles 

 in a person of apparently perfect health and vigor. Healthy men 

 should never feel sure that they will not die of an acute or chronic 

 catarrhal pneumonia, proceeding from a cold, and resulting in caseous 

 infiltration and destruction of the pulmonary substance. 



That feeble and ill-nourished persons should be in far greater dan- 

 ger of becoming consumptive than vigorous, well-nourished ones, will 

 not appear extraordinary from this point of view. 



Daily experience teaches us that a bad state of nutrition is usually 

 accompanied by a feeble power of endurance of noxious influences. 

 Even without especial knowledge of the fact, it is usually assumed, 

 a priori, that feeble, badly-fed persons are "sickly" that they are 

 especially prone to disease, and that they do not recover as rapidly 



