l]SS LOCAL TLSSIJE REACTIVITY 



nil KKIAIION OF THE J'FIFNOMKNON OF LOCAL TISSUE REACTIVITY 

 TO MIXED AND SECO^'I)AR^ INFECTIONS 



As (k'S(iil)C(l ill the basic cx]:)ci iiiiciils, the susceptibility iii- 

 diued by tiie active principles oi the phenomenon inicler con- 

 sideration or by active infection \vith a bacterinm makes a tissue 

 recej)tive to the injinTous effect of a hnge group ol biologically 

 unrelated active principles. These observations, then, bring out 

 the conception of synergistic effect of bacterial infections. One 

 is always impressed by the fact that the complications of acute 

 infectious diseases are produced by microorganisms luirelated to 

 the etiological agents responsible for a gi\cn infectious disease 

 itself. There exist in tiie experimental and clinical literature 

 almost innumerable examples of infections produced by a com- 

 bination of microorganisms apjjarently luirelated to each other. 

 Nattnally, ^vhenever j^ossible. a differentiation should be made 

 bet^veen the so-called mixed and secondary infections. 



As stated by Seitz (1929) , by the use of the term "mixed" in- 

 fections, one ^vishes to impart the impression that a given 

 infection is produced by a concerted effect of more than one etio- 

 logical agent. The idea that a comparatively large group of dis- 

 eases may be due to such mixed infections fuids its ^vay rapidly 

 into the literattne. The best examples are those of hog cholera, 

 swine influenza and possibly human influenza. 



In s\\ine fever or hog cholera, B/icilliis suipestilcr of the para- 

 typhoid group ^vas closely studied by Theobald Smith. The or- 

 ganism ^vas in\ariably foiuid in the intestinal necrotic lesions 

 and 'vvas considered as the primary etiological factor of the dis- 

 ease. Sch^veinitzer and Dorset (quoted by Seitz) sho^ved that the 

 disease is due to a filterable \irus. The virus disease is that of 

 diarrhea, vomiting and exanthematous eruption. If the anima! 

 survives following this acute attack,, the picture is comj^licated 

 by a severe pneumonia and intestinal idcerations, the intestinal 

 lesions being produced by B. suipestijer and the liuig infection 

 by B. suisepticus of the hemorrhagic septicemia group. The asso- 

 ciation of these t^vo microorganisms a\ ith the \irus of s^vine fever 

 is more than casual becairse it invariably a]:)pears in surviving 

 pigs. One really could take this disease as an example of a con- 

 certed pathogenic effect of two or possibly three etiological agents. 



A still clearer demonstration of a combined etiological role 

 of a virus with a gram-negative bacillus was made recently by 



