168 



CONTAGIOUS DISEASES. 



These very confident conclusions of Dr. Yeo, if allowed to go 

 unchallenged, are calculated to lead to much misapprehension, 

 and even to actions at law. They prove to me that he has had 

 but little or no opportunity of studying the disease in the living 

 animal, and that he bases his conclusions upon what he has 

 observed in the laboratory. 



Now, if pleuro-pneumonia were a species of bronchitis, or, as 

 he puts it, if the virus acted primarily on the bronchial mucous 

 membrane, one would naturally conclude that the bronchial 

 walls would in the earliest stages show evidence of disease ; but 

 such is not the case, and only occasionally do we meet with 

 congestive patches along their course in those parts of the lungs 

 already involved in the disease. As the disease advances, 

 however, the bronchi, as shown by Dr. Yeo in the woodcut, 



Figs. 3 and 4. — Transverse section of Broncho-vascular System, 

 contrasting the healthy with the diseased state. 



A. State of advanced disease. A. Artery, partially occluded by a 

 thrombus. B. Bronchus, contracted and plugged. V. Vein. C. Common 

 broncho-vascular sheath, thickened by exudation. I. Interlobular tissue. 

 P. Lobular parenchyma. 



B. A corresponding broncho-vascular system in health. ^ — (Yeo.) 



1 The cut was 'kinclly sent me by Dr. Fleming. 



become occluded, their walls invaded by the inflammation, and 

 they, as well as the blood-vessels, alveoli, and air cells, are filled 

 with a solid exudate, differing, however, from that of bronchitis, 

 where the occluding material is composed of more or less fluid 

 catarrhal products ; and one most important condition is 

 absent, namely, the blood-vessels of the inflamed lobules are 

 not occluded by coagula as in pleuro-pneumonia contagiosa. 

 In some instances, rarely met with since early slaughter has 

 been made compulsory, the bronchial tubes of a non-invaded 



