Inflammation and Related Phenomena 129 



other changes associated with inflammation, transient leucocytosis 

 occurs frequently as a physiological phenomenon, e.g. after mus- 

 cular exertion, both voluntary and involuntary, fear, mental stress 

 generally and prolonged mental concentration. Leucocytosis occurs 

 also in pathological situations in which inflammation or tissue de- 

 struction are absent, e.g. acute haemorrhage and profound chilling. 



These observations suggest that the polymorphonuclear leuco- 

 cytes detected in the above circumstances may be associated with 

 the concept of "stress." It is suggested that stress leads to release of 

 adrenaline which in turn stimulates the pituitary to release ACTH 

 which in turn stimulates the release of glucocorticoids from the 

 adrenal cortex (Selye, 1950) . In fact, adrenaline, ACTH and corti- 

 sone all cause a polymorph leucocytosis if injected into suitable 

 animals. Hypothalamic stimulation in one of a pair of parabiotic 

 rabbits leads to a polymorph leucocytosis in both animals, the re- 

 sponse being abolished by section of the splanchnic nerves (Rose- 

 now, 1951) . This result is consistent with neurogenic stimulation 

 of the adreno-pituitary system but also with the release of marrow 

 stimulating substances from other organs, e.g. liver (Beer, 1948) 

 and also with direct neurogenic activation of the bone marrow. 



In the polymorph leucocytosis associated with inflammation 

 similar mechanisms may be operative. It seems unlikely, however, 

 that other factors fail to play a part, especially in view of the sus- 

 tained nature of the leucocytosis seen, e.g. in some infections. 



The polysaccharides and lipopolysaccharides known as bacterial 

 endotoxins cause leucocytosis (preceded by leucopenia) on injec- 

 tion into rabbits. It is possible that bacterial protein, too, may be 

 involved since this material also causes neutrophil leucocytosis on 

 injection. The effect may be indirect and mediated through the 

 nervous system since narcotics have been claimed to abolish this 

 effect. Milk is probably more effective than bacteria as a leucocy to- 

 sis-promoting factor, so that foreign substances in wide variety may 

 share this property. Tissue extracts in general have not been found 

 to cause striking leucocytosis although nucleic acids possess some 

 ability to do so. Extracts of leucocytes with powerful pyrogenic 

 properties (see above) do not cause significant leucocytosis. Menkin 

 has found certain fractions of inflammatory exudates to cause 



