RESERVE FORCE AND ADAPTATION 165 



. Here I can do little more than mention certain general laws 

 which seem to be at work in bringing about, or favouring, 

 individual adaptation. 



1. The first is that of reserve force. No cell — and no tissue — 

 normally is in action to the limit of its powers ; on the contrary, 

 normal activity is far below what the cell is capable of perform- 

 ing. In other words, normal stimuli do not induce a maximal 

 reaction, and, therefore, irritants — excessive stimuli — up to a 

 certain limit, do not overwork, and do not lead to disintegra- 

 tion of the cell. Perhaps the greatest difficulty encountered by 

 most students of medicine in accepting the facts of phagocytosis 

 lies in this, that, regarding the tissues as normally sterile, they 

 cannot comprehend the assumption of what appear to be totally 

 new properties by the leucocytes and other cells in inflammation 

 and infection, namely, the assumption, as they regard it, of 

 phagocytic powers and the taking up of pathogenic bacteria. 

 But, as a matter of fact, this is no new property. Throughout 

 life the cells are engaged in digesting bacteria. We find phago- 

 cytic leucocytes passing out and free upon mucous surfaces — 

 any smear or swab from the pharynx will show these leucocytes 

 with their contained bacteria. As Ruffer, 1 Nicholls, 2 and 

 others have shown, bacteria are to be seen in the lymph-glands 

 and along the lymphatic channels of healthy animals, and these, 

 most often, within cells. As Ford, 3 working in my laboratory, 

 has demonstrated, using the fullest precautions against con- 

 tamination, bacteria can be cultivated from the liver and kidneys 

 of more than 50 per cent of the apparently healthy animals of 

 the laboratory ; and that the bacteria so obtained are not con- 

 taminations is proved by the remarkable regularity with which 

 these organs of each different species present a different bacterial 

 flora. Having followed Ford's observations and seen the care with 

 which they were conducted, I cannot accept the observations of 

 those who refute his work. As Wrosczek 4 has recently shown, if 

 animals be fed with non-pathogenic germs, or germs setting up 

 no recognizable intestinal disturbances, colonies of the species 



1 Ruffer, Brit. Med. Journ., 1897, i. 1177. 



2 Nicholls, Journ. of Med. Research, 1904, xi. 455. 



3 Ford, Journ. of Hygiene, 1901, i. 277, with series of tables in Trans. 

 Assoc. Am. Phys., 1900, xv. 389. 



4 Wrosczek, Arch, polonaises d. sc. biol. et mid., 1903, ii. 1796 (Ref. Journ. 

 de physiol. et path, gen., 1904, vi. 385). 



