S 4 POPULAR SCIENCE MONTHLY 



acteristics of an organic enzyme. It digests the fat; it rebuilds fat 

 from the component parts, i. e., its action is reversible; it is affected 

 similarly by temperature changes and chemicals. 



Another parallelism exists between the " vital " and inorganic phe- 

 nomena, in the action of the salivary juice and acids on starch. The 

 starch is to a greater or less extent digested in the mouth by virtue 

 of a starch-splitting enzyme of the saliva. The same thing occurs if 

 the starch and saliva are put together in a test tube. Acids will also 

 digest starch. There is one marked difference, however, between the 

 two. Enzymes act best at body temperature or a little above, while 

 acids require boiling for their optimum action. 



The temperature at which ferments act best is usually a little above 

 the temperature of the body to which they belong. The optimum 

 temperature for the action of enzymes of cold-blooded animals is below 

 that for warm-blooded animals. A rise of twenty or thirty degrees 

 above the optimum temperature destroys the ferments. A lowering of 

 the temperature unless to the extreme does not kill; it only inhibits. 

 The enzymes regain their function when the temperature returns to 

 normal. 



Many drugs have a very decided influence upon the fermentative 

 processes. Of recent years this problem has occupied the mind and 

 time of a number of physiologists. It is evident that this is a question 

 of vital importance, on account of the general distribution of enzymes 

 in the body, and the common introduction of drugs into the body. 

 Very much too little is known, by even the scientific physician of to-day, 

 regarding the action of drugs on the enzymes of the body. Some 

 chemicals when present with the enzyme increase its power to do work; 

 others decrease its power; and others stop it entirely. The concentra- 

 tion of the chemicals is of paramount importance. Most chemicals 

 in concentrated solutions entirely prevent the action of ferments. 

 On dilution the inhibitory power of the solutions decreases. In mod- 

 erate concentrations some inhibit, more or less, and some stimulate, 

 more or less. Both these processes usually decrease as the concentra- 

 tion of the respective solutions decrease. In some cases an effect may 

 be noted in even very dilute solutions; a good example of such a 

 solution is hydrocyanic acid. 



If the author has been successful in the presentation of this subject, 

 the reader should be impressed with the importance of the problem. 

 The intimate relationship of enzymes with the vital processes renders 

 an extensive knowledge of these bodies fundamental in the research 

 into the phenomena of life. 



