CROUPOUS PNEUMONIA 487 



pneumococcus was proved to be present in the saliva 

 of the animals for a month after the spraying. The 

 failure to produce pneumonia by spraying suggests that 

 some special factors are necessary for the invasion of the 

 bronchi and consequent pneumonia, but what these are 

 is uncertain. It is of interest that pneumococci are not 

 infrequently present in the saliva of normal individuals, 

 and the relationship of " catching cold " to an attack of 

 pneumonia may in some cases be a lowering of vitality 

 of the tissues rendering them vulnerable to the attack 

 of the pneumococcus already in close proximity to 

 them. 



Pneumococci may be found in the blood of the experi- 

 mental animals in from six to twenty-four hours after 

 intratracheal inoculation and frequently before the 

 occurrence of any symptoms. Subcutaneous or intra- 

 venous inoculation resulted in a septicaemia without any 

 evidence of pneumonia or of pulmonary localisation. A 

 spontaneous outbreak of pneumonia among monkeys 

 was observed (thirty -eight cases), the pneumococcus 

 present being of Type IV. 



Blake and Cecil consider that croupous pneumonia is 

 primarily an interstitial infection of the lung. The pneu- 

 mococcus primarily invades the tissue of the lung at some 

 point in the lobe proximal to the hilum, spreads throughout 

 the lobe by the perivascular, peribronchial and septal 

 interstitial tissues and tymphatics, quickly reaching the 

 pleura, and invades the alveolar structure primarily by 

 way of the alveolar walls. 



Paihogenicity . The S. pneumonice is the cause of acute 

 croupous pneumonia in man, whether primary or secon- 

 dary in the course of other diseases, and occurs in large 

 numbers in the rusty sputum and hepatised lung, and 

 in 20 per cent, of the cases can be isolated from the blood 

 if 5-10 c.c. be cultured. In America the disease has of 



