62 The Lung Plague of Cattle. 



lar infiltration into the connective tissue around the air 

 tubes and their accompanying vessels, and in the hepa- 

 tized lung this is always seen as a thick, firm, resistant 

 white material, having the compressed and contracted 

 and often plugged air tubes and vessels in the centre. 

 (See Heliotype.) These thickened masses have already 

 been referred to as standing out in stalactite form from 

 the inner wall of the sac in which the dead (necrosed) 

 lung is undergoing solution. 



Nature of the Bovine Lung Plague. 



That the plague is determined by an infecting materia] 

 conveyed from beast to beast there can be no doubt. The 

 intimate nature of this material has never been deter- 

 mined. No special anatomical element, no specific organ- 

 ism of animal or vegetable origin has been detected as 

 constant in the diseased organ and peculiar to it. Yet 

 tlie presence of a specific contagium is demonstrated in all 

 our experience of the disease as above recorded, and in 

 the prophylactic value of inoculation to be referred to 

 below. This infecting material, as will be seen by 

 the records of inoculation, rarely affects the lungs 

 when first lodged on a raw surface of some other part 

 of the body, differing in this essentially from most other 

 specific disease poisons which have a definite seat of elec- 

 tion in which their morbid processes are invariably es- 

 tablished, no matter by what channel they may have en- 

 tered the body. Since the lung plague contagium does 

 not usually affect the lungs when introduced by some 

 other channel it follows almost of necessity that when it 

 does attack the lungs it must have been introduced into 

 these direct. If it has been inhaled in the air it will fall 

 upon one of two points — -the air tubes, or the air cells — 

 and there begin its baleful course. This is exactly in ac- 

 cordance with the early lesions as described above. 



1. If arrested, as it most commonly will be, in the air 



