THE FOCAL REACTION 77 



we are familiar. But, from analogous studies in focal reactions else- 

 where it must be assumed that, with proper dosage, the positive phase 

 and the increased tendency to healing follows about the lung focus 

 just as it does about a joint lesion that can be objectively studied. 

 In this duality of the reaction lies the usefulness of the focal reaction 

 as a therapeutic measure. 



Mechanism of Focal Reaction. VASCULARIZED INFLAMMATORY 

 Foci. During the course of the past five years we have become fa- 

 miliar with the biological alterations that take place in the organism 

 after tuberculin injections as well as after the so-called nonspecific 

 agents. These changes, described in the preceding chapter, are nu- 

 merous and complex but the more important can be placed in two 

 groups: (1) those that deal with cellular stimulation, and those 

 (2) that result primarily from alterations in the permeability of the 

 cells. 



The former have been broadly included by Weichardt under the 

 term "Plasmaactivation." Under the stimulus of moderate doses of 

 nonspecific agents cellular activity is markedly increased. This finds 

 its expression in increased secretory activity of gland cells, increased 

 activity of muscle cells (myocardium), increased activity of leu- 

 kocytes (phagocytosis), etc. The changes that take place in the 

 permeability of the cell membrane have been studied by Luithlen, by 

 Starkenstein and others and represent a decidedly diphasic phenomenon. 

 The permeability of (the capillaries is first increased as evidenced in 

 the great increase in the lymph flow and in the concentration of the 

 blood; the permeability of the tissue cells is increased with a re- 

 sulting outpouring of enzymes, of fibrinogen and prothrombin, of 

 immune bodies, etc.; the increased permeability of the nerve cells is 

 associated with a lowering of the threshhold for nervous impulses 

 and becomes manifest clinically in increased susceptibility to pain, 

 general irritability, headache, etc. When this first phase has passed 

 compensation takes place in a lessened permeability of the cells, with 

 effects that are to be anticipated lessened susceptibility to intoxi- 

 cation, lessened nervous irritability lessened exudation a lowering 

 of enzyme concentration, etc. 



Numerous other observations have been made that are, in my 

 opinion, subordinate in interest to these two fundamental alterations 

 in the permeability of the cell membranes and the general stimulation 

 of the protoplasm. 



With these considerations in mind we can approach the study of 

 the mechanism possibly involved in the focal reaction about inflam- 

 matory tissues from a relatively simple point of view. 



In an inflammatory focus supplied with highly vascularized gran- 

 ulation tissue the systemic effects of a tuberculin injection or the in- 

 jection of a nonspecific agent will bring about (1) an increase in 

 the exudation of fluids with increased redness and swelling because 



