CROUPOUS PNEUMONIA. 167 



m*ong, however, to regard all cases of this disease, which supervene 

 upon some chronic malady, as belonging to the secondary form. 



The liability to primary croupous pneumonia exists at all periods of 

 life, down to extreme old age. It is rare, however, among infants at the 

 breast, and in the first years of childhood. Males are attacked more fre- 

 quently than females ; not, however, because vigorous, full-blooded per- 

 sons are peculiarly subject to the disease. The latter, indeed, are by 

 no means exempt ; but feeble and broken-down subjects, convalescents 

 from grave diseases, individuals who already have repeatedly suffered 

 from pneumonia, are, perhaps, more liable to be attacked than the 

 robust ; and pneumonia often complicates diseases which have already 

 effected an impoverishment of the blood, with emaciation and consti- 

 tutional exhaustion. Very many of the inmates of hospitals, sufferers 

 from inveterate disease, finally succumb to intercurrent pneumonia. 



Its exciting causes are generally unknown. At times pneumonia 

 becomes of very frequent occurrence, while croup, acute articular rheu- 

 matism, erysipelas, and other acute inflammatory disorders prevail at the 

 same time, attacking their victims without any obvious provocative. 

 This prevalence of acute inflammatory disease through the operation of 

 unknown atmospheric and telluric agencies is generally spoken of as 

 inflammatory epidemic influence. We particularly observe the epi- 

 demic occurrence of pneumonia in severe and protracted winters during 

 the prevalence of a northeast wind. Sometimes, however, it arises 

 under conditions precisely the reverse. The statistical statements as to 

 the greater frequence of pneumonia in northerly and elevated localities 

 have, of late, been regarded as untrustworthy. 



Direct irritants acting upon the lungs, the inhalation of very cold or 

 very hot air, foreign bodies, which have entered the air-passages and 

 stopped up a bronchus, fractures of the ribs, wounds of the thorax, may 

 be counted as among the exciting causes, although scarcely any of these 

 conditions are found to exist in one case of pneumonia out of fifty. Nor 

 is the croupous form of the disease often found to attack the parts 

 about a morbid growth or around a haemorrhagic infarction. 



With regard to the influence of cold, it is difficult to decide in indi- 

 vidual instances whether the attack has been preceded by an exposure 

 to cold more severe than that to which the patient has repeatedly 

 exposed himself with impunity. Opinions, therefore, are divided as 

 to the effect of cold in producing pneumonia. 6 



ANATOMICAL APPEARANCES. Croupous pneumonia almost always 

 attacks a somewhat extensive portion of the lung, commencing usually 

 at the root, and spreading thence to the lower and afterward to the 

 upper lobes. Sometimes an entire lung is inflamed, or the process may 

 extend into the other lung, producing a double pneumonia. It is 



