Formaldehyde, hydrocyanic acid, and soluble fluorides usually inhibit both the activity of a cell and of the enzymes which it contains; while other antiseptics, such as toluene, xylene, etc., prevent the growth of the cell, or organism, without interfering with the activity of the enzymes which may be present. By the use of this latter type of antiseptics, it is possible to distinguish between chemical changes which are involved in the actual development of a cell and those which can be brought about in other media by means of the enzymes which are contained in the cell. Any substance which increases the catalytic activity of an enzyme is known as an "accelerator," or "activator"; while one which prevents this activity is called an "inhibitor," or "paralyzer." A type of accelerating influence quite different from that of electrolytes is found in the effect of certain amino-acids upon enzyme action. The influence of small amounts of asparagine in enormously increasing the hydrolytic effect of amylase is an example. There is no known explanation for this type of activation of the enzyme. The influence of activators, or inhibitors, in providing favorable or unfavorable conditions for the action of an enzyme, should not be confused with the relation to the enzyme itself of what are known as "coenzymes" and "antienzymes," discussed in the following paragraph. COENZYMES AND ANTIENZYMES In the cases of many enzymes of animal tissues, it has been found that they are absolutely inactive unless accompanied by some other substance which is normally present in the gland, or protoplasm, which secretes them. Thus, the bile salts are absolutely necessary to the activity of trypsin, in its characteristic protein-splitting action. Such substances are known as "coenzymes." They can usually be separated from their corresponding enzymes by dialysis, the coenzyme passing through the parchment membrane. Such coenzymes are not killed by boiling the dialyzate, and the activity of the enzyme is restored by adding the boiled dialyzate to the liquid which remains within the dialyzer.