DEVELOPMENT OF THE GERM THEORY. 27 



Lister, with a combination of experimental resource, patience, 

 and brilliancy, almost unparallelled in the history of surgical 

 science, step by step, built up a theory and practice of antiseptic 

 surgery — a theory and practice which rapidly revolutionised 

 the treatment of wounds and the routine of ward management. 

 He introduced a system which has affected the practice, not only 

 of those who believe in its accuracy, but of those who cannot 

 accept all the details, yet have nevertheless adopted its principles. 

 He proved conclusively, and his proofs have been confirmed by 

 many others, that ordinary cleanliness in the dressing of wounds, 

 either made or treated by the surgeon, was not sufficient ; but that 

 the use of some kind of antiseptic was absolutely necessary to 

 avoid the risk of septic infection. Surgery and its subjects owe to 

 Lister a debt which can never be repaid. 



These germs may also find an entrance through the skin and 

 hair follicles, and give rise to localised centres of infection, such 

 as boils, carbuncles, and different forms of cellulites, or they may 

 be swallowed or inhaled, be taken up and circulated by the leuco- 

 cytes, and deposited at any seat of injury or irritation, and as 

 these germs are constantly present under ordinary conditions of 

 life, their effects would certainly be much more constantly in evi- 

 dence were there not some natural safeguarding influence. It has 

 long been known that certain cells in the living body are capable 

 of removing absorbable aseptic substances, such as cat-gut liga- 

 tures, etc. Metschnikoff introduced the term phagocytosis to 

 designate the process by which the leucocytes and other cells 

 destroy or digest pathogenic micro-organisms, and the cells which 

 perform these functions he calls phagocytes. The leucocytes are 

 the ordinary police intrusted with the duty of taking up unautho- 

 rised intruders, but in moving them on sometimes they let them 

 escape. But the other cells — the mucous corpuscles, connective 

 tissue, cells, endothelia of blood-vessels, and lymphatic vessels, 

 alveolar epithelium of the lungs and the cells of the spleen, bones, 

 marrow, and lymphatic glands — may all be enrolled as special 

 constables to repel an invasion in force. When the struggle 

 between a microbe and a phagocyte turns out in favour of the 

 latter, the microbe does not multiply in the protoplasm, or ceases 

 to do so before the protoplasm is destroyed, and as the microbe 



