ANATOMICAL CHANGES 479 



remarkable powers of resistance against cold ; it has been exposed 

 to a temperature several degrees below freezing-point without 

 I iri ng killed. Experiments on the effects of drying have given 

 somewhat diverse results, but as a rule the organism has been 

 found to be dead after being dried for from six to eight days, 

 though sometimes it has survived the process for a longer period ; 

 exposure to direct sunlight for three or four hours kills it. When 

 cultivated outside the body the organism often loses its virulence, 

 but some races remain virulent in cultures for a long period of 

 time. 



Anatomical Changes and Distribution of Bacilli. The 

 disease occurs in several forms, the bubonic and the pulmonary 

 being the best recognised ; to these may be added the septiccemic. 

 The most striking feature in the bubonic form is the affection 

 of the lymphatic glands, which undergo intense inflammatory 

 swelling, attended with haemorrhage, and generally ending in 

 a greater or less degree of necrotic softening if the patient lives 

 long enough. The connective tissue around the glands is 

 similarly affected. The bubo is thus usually formed by a 

 collection of enlarged glands fused by the inflammatory swelling. 

 True suppuration is rare. Usually one group of glands is 

 affected first, constituting the primary bubo in the great 

 majority the inguinal or the axillary glands and afterwards 

 other groups may become involved, though to a much less 

 extent. Along with these changes there is great swelling of 

 the spleen, and often intense cloudy swelling of the cells of the 

 kidneys, liver, and other organs. There may also occur secondary 

 areas of haemorrhage and necrosis, chiefly in the lungs, liver, 

 and spleen. The bacilli occur in enormous numbers in the 

 swollen glands, being often so numerous that a film preparation 

 made from a scraping almost resembles a pure culture (Fig. 

 141). In sections of the glands in the earlier stages the bacilli 

 are found to form dense masses in the lymph paths and sinuses 

 (Fig. 145), often forming an injection of them; they may also 

 be seen growing as a fine reticulum between the cells of the 

 lymphoid tissue. At a later period, when disorganisation of 

 the gland has occurred, they become irregularly mixed with the 

 cellular elements. Later still they gradually disappear, and 

 wlp.-ii necrosis is well advanced it may be impossible to find any 

 a point of importance in connection with diagnosis. In the 

 spleen they may be very numerous or they may be scanty, 

 according to the amount of blood infection which has occurred ; 

 in the secondary lesions mentioned they are often abundant, 

 lu the pulmonary form the lesion is the well-recognised "plague 



