134 IMMUNOLOGY 



resistance has been investigated extensively the problem of sus- 

 ceptihility mechanisms has been neglected, shonld stimnlate re- 

 search of great value to scientific medicine. The results of their 

 experimental studies may be summarized as follows : 



1. They suggest that the inoculation of the chorio-allantoic mem- 

 brane of the chick embryos with pure cultures of bacteria is an 

 excellent method for studying the early stages of invasion. 



2. They produced experimental infections with Staph, aureus, 

 Str. haemohjticus, Str. viridans, and A. aerogenes, E. typkosa, 

 Br. abortus, C. diphtheriae, and 3Iyco. tuherculosis avium. 



3. They found that either mesodermal cells (fixed or motile), 

 or epithelial cells, or both, seem to act as host-cells for all of the 

 organisms mentioned except Stajyh. aureus, Str. haemohjticus 

 and C. diphtheriae. Str. virid/ms utilized the intracellular en- 

 vironment of wandering and fixed mesodermal cells; A. aerogenes 

 the wandering mesodermal and entodermal cells; E. typhosa 

 utilized cells of the ectodermal epithelium ; Br. abortus utilized 

 both ectodermal and mesodermal cells while Mj/co. tuherculosis 

 avium preferred mesodermal elements. 



The staphylococcus and hemolytic streptococcus grew well in 

 between the tissue cells and underwent phagocytosis but were ap- 

 parently unable to utilize any living intracellular environment 

 for growth. 



4. These results caused Goodpasture (1937) to investigate care- 

 fully the pathogenesis of typhoid fever. As a result of his study 

 of excellent autopsy material he found young plasma cells in sec- 

 tions of the lymphoid follicles of iliac and mesenteric lesions filled 

 with small, gram-negative apparently unaltered bacilli which he 

 judged to be E. typhosa. He found larger gram-negative bacilli 

 in microphages of the lesions associated with remnants of lympho- 

 cytes and macrophages. Goodpasture suggests that the young 

 plasma cell is a host for E. typhosa in human cases and nourishes 

 and protects the bacteria during the incubation period and through- 

 out the. disease. 



Role of Clasmatocytes in Other Infections. — That the reticulo- 

 endothelial system is an important factor in combating both bac- 

 terial and protozoan infection is suggested by the results of a 

 number of investigators. Buxton (1907) concluded that the re- 

 sistance of rabbits immunized against typhoid is due largely to 



