ENZYMES 455 



the edge of the blot. If a mixture of a cadmium salt with 

 one of silver, lead, or mercury is treated in the same way a 

 patch of black sulphide in the centre is surrounded by a yellow 

 ring, showing that the metallic ions travel to different distances 

 and spread themselves to different extents over the surface of 

 the paper fibre, and that they all behave differently from water. 1 



Similar observations have been made on salts of barium and 

 calcium as compared with those of potassium. 2 



The whole subject of enzyme action is, however, still under in- 

 vestigation by a considerable number of chemists and physio- 

 logists ; in fact it forms part of a new and extensive department of 

 organic chemistry which is usually designated " biochemistry " in 

 allusion to its close association with the phenomena of living 

 beings, vegetable or animal. Any survey of the phenomena 

 exhibited by enzymes cannot fail to excite wonder at the powerful 

 action of these complex and sensitive agents. They are capable 

 of bringing about changes which can be effected by ordinary 

 chemical agents, such as strong acids or alkalis, only under 

 circumstances of considerable concentration or high temperature. 

 The hydrolysis of a fat for example can be accomplished either 

 by boiling with alkali, when a soap is produced, or by steam, 

 heated considerably beyond the boiling point of water, when 

 glycerin and a fatty acid are produced. The enzyme lipase can 

 do its work without sensible rise of temperature, and remains 

 active after all is over. Invertase (from yeast), according to 

 O'Sullivan and Tompson, can change 100,000 times its weight 

 of cane sugar into glucose and fructose, and can still go on 

 producing inversion, an effect enormously in excess of that 

 produced by sulphuric acid at the same temperature. 



In fact the metaphor already made use of to illustrate the 

 specific action of enzymes may be extended a little in order to 

 emphasise the contrast between the operation of these substances 

 and the accomplishment of the same chemical change by ordinary 

 chemical agents. For suppose it is desired to enter a house the 

 action of the former may be compared to the simple and peaceful 

 process of inserting the right key into the lock, the action of the 

 latter would be more nearly represented by breaking down the 

 door. 



The effects described here are nearly all brought about by the 



1 T. Bay ley, Trans. Chem. Soc., 1878, p. 304. 

 * Schunbein. Poggend'-rfs Ann., 1861, p. 275. 



