i THE ESSENTIAL CAUSE 7 



scopic examination alone of the gland juice is sufficient to 

 assert that the analysis is pointing in a distinct manner 

 to plague, viz. great abundance of Gram-negative, bipolar- 

 stained bacilli all of the same aspect ; subsequent culture 

 and animal experiment should complement the analysis and 

 definitely prove the case to be one of plague. Further 

 inquiry by the epidemiologist leaves no doubt about the 

 correctness of the diagnosis. 



Sections through the inflamed glands show, on micro- 

 scopic examination, the following condition : — The tissue 

 around the gland is highly cedematous, some lymph vessels 

 containing leucocytes, red blood corpuscles, and numerous 

 B. pestis ; the veins and capillaries are distended and filled 

 with coagulated blood ; amongst the blood corpuscles are 

 numerous B. pestis. The afferent lymph vessels are filled 

 with coagulated lymph — leucocytes and fibrin — and crowds 

 of B. pestis, some of the vessels showing thrombi almost 

 entirely composed of B. p>estis. The cortical sinuses are 

 distended and densely packed with B. pestis, so are many 

 of the medullary lymph sinuses, besides containing blood 

 corpuscles ; the lymphatic tissues of the cortical and 

 medullary portions contain a large amount of extra vasated 

 blood ; in many parts the lymph tissue is broken down, 

 necrotic, and is not easily stained ; numerous B. pestis are 

 found in it. The efferent lymph vessels are distended by, 

 and filled with, coagulated lymph, numerous blood cor- 

 puscles, and masses of B. pestis. In a subsequent chapter 

 we shall reproduce a photogram of a section through the 

 inflamed lymph gland of a rat inoculated with plague 

 bacilli cutaneously at the root of the tail ; the illustration 

 may be taken likewise as a faithful representation of the 

 bubo as it occurs in man. 



