NITROGENOUS OKGANIC CELL-CONSTITUENTS. Ill 



will be considered under tine study of the individual ferments in the 

 section on Digestion, they are amorphous, colorless powders, which are 

 highly soluble in water, resemble gums somewhat in appearance, and are 

 precipitated from their solutions by alcohol, corrosive sublimate, and 

 lead acetate. One of their remarkable points of contrast to albuminous 

 bodies is that, when precipitated from solution in water or glycerin by 

 absolute alcohol, if the precipitates are filtered off and dried, they are 

 again perfectly soluble in water, and are still capable of exerting all their 

 actions ; hence, their precipitation is more of a mechanical nature than 

 chemical. Further, when the precipitates formed by the above reagents 

 are decomposed hy sulphuretted hydrogen a watery extract of the pre- 

 cipitate will still preserve the original properties of the ferment ; in other 

 words, the soluble matter is restored to the water unchanged, and still 

 preserves its specific properties. The ferments are with difficulty freed 

 from albuminoids, and it is in all probability the albuminoid which is 

 chemically precipitated from their solutions by the above reagents, and 

 which in this precipitation carries with it mechanically the ferment. 

 Consequently, this propert}^ of the ferment of being precipitated by the 

 above reagents is dependent upon the albuminous bodies which are 

 nearly always associated with it. We shall, further, find that this prop- 

 erty of being carried clown Iry precipitates from solutions is the basis 

 of nearly all the methods which have been employed for the isolation of 

 the different digestive ferments. 



Ferments obtained from the animal and vegetable kingdom may 

 have the most varied functions. We have but little information 

 concerning the soluble ferments from a chemical point of view. We 

 do not even know whether they all have the same chemical compo- 

 sition, and differ only in some unknown manner in their specific activity. 

 They only are active at a temperature below 60° C, and when in the 

 presence of water ; at the temperature of boiling water they are perma- 

 nently destroyed ; at lower temperatures their activity is suspended. 

 They do not themselves appear to be influenced in the phenomena of fer- 

 mentation which they inaugurate ; ferments are also inactive in the pres- 

 ence of various chemical agents, such as alcohol, the stronger mineral 

 acids, and all the large group of substances which are known as antisep- 

 tics. Ferments may lie of two kinds ; either organized ferments, such 

 as the yeast-plant, malt, vibrios, bacteria, etc., — substances which are 

 themselves elementary, cellular organisms, — or the so-called unformed 

 ferments, or enzymes, substances which invariably originate in the interior 

 of animal and vegetable protoplasm, and are soluble and not organized. 



This latter group comprises all the ferments with which we are par- 

 ticularly interested. Their specific action is in many cases closely analo- 

 gous to that of the formed ferments. There are, however, several points 



