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 phenomena, 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 concentration 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 moderate concentrations some inhibit, more or less, and some stimulate, more or less. Both these processes usually decrease as the concentration 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.