K. F. Meyer 4^ 1 



cytoplasmic existence during its parasitism and, if so, in what cells? Compara- 

 tive studies of infection of the goat udder, the chick embryo, and now of the 

 tissues of man strongly suggest that the mesenchymal and possibly the ecto- 

 dermal layers are host cells for the brucellas. Very acute infections lend them- 

 selves to a demonstration of this stage of the parasitism. With the progress of 

 the disease, the phagocytic activities in the reticulo-endoihclial beds, the in- 

 flammatory reaction to the necroses in the organs damaged by the bacteria, or 

 the split products of the allergic inflammation create microscopic pictures in 

 which the early phases are either not discernible or so widely scattered that it 

 is impossible to find them without examining serial sections. 



In the interest of a clearer understanding of the pathogenesis, it is obviously 

 desirable to study acute Brucella infections exhaustively. In the subacute or 

 protracted disease stages one finds either no lesions (certain questionable au- 

 topsy reports indicate absence of organ changes while a few show specific 

 evidence of invasion) or the "tuberculoid nodules" or "granulomas," which 

 may be interpreted as characteristic. The factors which guide the formation 

 of these lesions are unkno^vn. They have all the markings of a defensive cellu- 

 lar mechanism and raise the following questions: Is it possible that the poly- 

 morphonuclear leucocytes ingest the free bacteria under the influence of the 

 opsonins and then become impotent, their place being taken by the monocytes, 

 which rapidly aiTange themselves into nodules in order to destroy the bacteria? 

 Do the brucellas, in part changed by the antibodies, lose their invasiveness 

 and merely act to incite specific granulomas as a foreign-body reaction? Are 

 these structures in some way connected with allergy? And finally in what man- 

 ner are the capsules of the brucellas related to these processes? (See Mickle.*°) 



The microscopic findings in the kidneys and the lymph nodes of D.S. have 

 shown that in the vicinity of the bacterial proliferation, either in the living 

 tubular epithelium or the necrotic cellular detritus, an intense proliferation 

 of the reticulo-endothelial cells took place. In the kidney this has occurred in 

 the intertubular connective tissue. The cellular types, which possess all the 

 properties of phagocytes, resembled the elements one finds in typhomas; they 

 are monoblasts— mono- or histiocytes— intermingled with lymphocytes. The 

 reasonableness is great that these lesions represent the early stages of the 

 granulomas, which through necrobiotic processes finally reach the structural 

 appearance seen and described in the majority of fatal Bang infections sub- 

 jected to autopsy within the first to the sixth month. AVhen the infiltration is 

 very large and the necrobiotic colliquation is extensive, typical purulent me- 

 tastases in a diversity of organs may be encountered. 



Undulant fever due to Br. abortus or suis is, in ilic majority of instances, 

 a relapsing bacteremia which may be interwoven with allergic manifestations. 

 Although the principal place of proliferation may be the spleen, it is apparent 

 that the bone marroAV deserves consideration. In a small percentage of infec- 

 tions, metastatic foci are formed in the spleen, liver, the lymph nodes, kidneys, 

 sex organs, bones, and central nervous system. Xecrobioiic processes in these 



