220 PHARMACEUTICAL BACTERIOLOGY 



same animal is most variable, depending upon the nature of the food 

 ingested, the stage of the digesting process, the acidity of the stomach, 

 abnormal or pathological conditions as in gastritis, cancer, etc. 



The "ingluvin" of the older pharmacopoeias and materia medicas, 

 is the pepsin ferment obtained from the gizzard of the domestic fowl 

 which, at one time, enjoyed an extensive use in medicine. The pepsin of 

 the dog is said to be the most active. That of the frog and of cold-blooded 

 animals generally, is less sensitive to cold. , For example, frog pepsin is 

 still active at o° C, whUe the pepsin of warm-blooded animals is inac- 

 tivated at io° C. 



Pepsin is not immediately elaborated in the so-called peptic cells of 

 the stomach, rather these cells form a proferment or pepsinogen which 

 in association with dilute free hydrochloric acid, is quickly converted into 

 pepsin. 



Pepsin has never been isolated in a pure state. In its comparatively 

 purest state thus far obtained it is a yellowish, brittje, homogeneous mass, 

 soluble in water and dilute solutions of acids, solutions of salts and in 

 glycerin. It is precipitated by alcohol and has the general properties 

 of enzymes. It is quickly inactivated by alkalies. In solutions it is 

 destroyed at a temperature of 55° to 57° C, while in the dry state it 

 can withstand a temperature of 100° C. 



Since the stomach cells contain pepsinogen very largely, the washed 

 stomach pepsin extract, as formerly prepared is comparatively inactive. 

 To determine the activity or digesting power of pepsin it is permitted 

 to act upon albuminous substances. Small amounts of pepsin dissolved 

 in dilute solutions of hydrochloric acid (o.io to 0.20 per cent.) are allowed 

 to act on egg albumen or fibrin. The time required for a unit amount of 

 the pepsin solution to digest a unit amount of the albumen at a given 

 temperature, uniform for all tests, indicates the activity of the pepsin. 

 Grunhagen permits a small mass of fibrin to become saturated with the 

 acidulated pepsin solution and then places the mass upon a filter. The num- 

 ber of drops of digested fibrin which pass through the filter in a given time 

 indicates the digesting power of the pepsin. Mett places small glass 

 tubes filled with coagulated albumen into the pepsin solution in an incubator 

 and notes the amount of albumen digested in ten hours. 



The action of pepsin is retarded by chloroform, strong solutions of salts 

 generally, particularly sodium chloride, and by ammonium sulphate. 

 Alcohol below 10 per cent, does not interfere with its action, while beer 

 even with only 3 per cent, alcohol retards its activity very much. Other 

 substances which retard pepsin digestion are wine, saccharin, tea and coffee 

 (due to tannin present), tobacco and strong solutions of alcohol. Weak 

 solutions of acids, small amounts of spices, very minute doses of arsenic, 



