ARTICLES 433 



that the protection is due to a " vital strength " is as nearly- 

 accurate as many modern ideas. 



Early observers, e.g. Claude Bernard, considered that the 

 protection was a mechanical one and was due to the rapid 

 shedding of the superficial epithelium and to the mucus which 

 was being constantly poured out. Weinland and others de- 

 scribe anti-ferments. Klug has suggested that the mucin forms 

 an adsorption compound with the enzyme. And Bayliss extends 

 the idea to food which may also adsorb the enzyme. Burge — 

 as already stated — considers that oxygen produced from the 

 catalase which is specially plentiful in the wall of the stomach 

 and intestine is the protective factor. 



The work and conclusions of Bolton (191 3) in relation to 

 ulcers of the stomach are very interesting on this point. He 

 showed that ulcer formation was in no way dependent on the 

 neutralisation of an anti-pepsin ; while Wolff in the same con- 

 nection found that the stomachs of patients who had suffered 

 from gastric ulcer contained no less anti-pepsin than normal 

 stomachs. 



It is clear therefore that more work must be done before 

 the exact nature of the anti-enzyme factor can be decided. 



Conclusion. — From this review of the recent work on enzyme 

 action, it will be seen that advance in knowledge of the subject 

 has been slow, and has involved much careful and tedious work. 

 An attempt has been made to show the stages which have been 

 reached in the various branches of the subject, and at the same 

 time to indicate, without undue formation of hypotheses, the 

 lines along which recent work would lead us to expect that 

 solutions of the many problems may be found. 



In the first instance, the value of a more exact knowledge 

 of the actual nature of enzymes is noted, although the subject 

 of the essay does not admit of it being dealt with in detail. 



The factors governing the velocity of enzyme action are shown 

 more and more to be capable of a physical explanation, so much 

 so that some have suggested that the whole of enzyme action 

 (even the nature of enzymes themselves) may be so explained. 

 The work of Beatty (19 16), although hypothetical, is very 

 interesting on this point. He puts forward a theory of enzyme 

 action which reduces it to the simplest possible explanation, 

 viz. that all the reactions concerned are essentially the addi- 

 tion or splitting-off of H* or OH* ions. The theory is an 

 advanced one, but certainly modern evidence tends in that 

 direction. 



The work on the synthetic action of enzymes has estab- 

 lished definitely that synthesis does occur, but much remains 

 to be done on the factors governing the reaction. 



Our knowledge of oxidation and other processes is seen to 



