Although, with the exception of a kind of pepsin in the naked protoplasm of aethalium septicum, a species of myxomycetes,1 enzymes have not been shown to be present in the protoplasm of the lowest organisms, it is probable that the processes of life in all living beings from the lowest to the highest are carried on by their means. A ferment, which is evidently of the greatest importance in the animal economy, has been recently discovered in the blood by Schmiedeberg. He has given to it the name of Histozyme, and he believes that its function is to split up nitrogenous substances preparatory to their oxidation.2 The chief enzymes are the following:-

Dlastatic Or

Amylolytic

Which convert starch and amyloids into maltose .

Diastase from malt.

Ptyalin from saliva.

Amylopsin from pancreas.

Other ferments having a similar action from other parts of the body.

Which convert maltose. into glucose . .

From small intestine.

Inversive Ferments

Which convert cane sugar into dextrose and levu-lose . . . .

Invertin from the intestinal juice.

„ ,, mucus of the mouth.

,, ,, tissue of the testis.

Which decompose gluco- sides . . . .

Emulsin from bitter almonds.

Myrosin from mustard.

Decomposing sugar .

Rennet.

Decomposing fats . .

From stomach.

From pancreas (Stearopsin).

Proteolytic Ferments

Which decompose proteids and form peptones .

Pepsin from stomach.

Trypsin from pancreas.

Others from saliva.

Histozyme.

The action of drugs on enzymes is ascertained by taking two portions of a solution containing the enzyme and the substance to be acted upon. To one of these a quantity of the drug to be tested is added, the other acts as a standard with which to compare it. If the drug is in solution, a corresponding quantity of water must be added to the standard solution in order that both may be alike. They are then placed in a warm chamber and the rapidity of digestion is noted.

1 Krukenberg, Untersuch. a. d. physiol. Inst. d. Univ. Heidelberg, Bd. II., 1878, p. 273.

2 Schmiedeberg, Arch.f. exper. Path. u. Pharm., Bd. xiv. S. 379.

The effect of some of the more important drugs on the action of enzymes will be readily seen from the following table from Wernitz, quoted by Meyer.1 In it the proportion is shown of the drugs which arrest in watery solution the action of enzymes; thus, one part of chlorine in 8,540 parts of a watery solution will arrest the action of ptyalin upon starch paste, while creasote has no action on it even in saturated solution, and corrosive sublimate is so enormously destructive as to arrest its action, even in one part in 52,000.

1 Hermann Meyer, 'Ueber das Milchsaureferment u. sein Verhalten gegen Antiseptica,' Inaug. Diss. Dorpat, 1880.

Emulsin

Myrosin

Diastase

Invertin

Ptyalin

Pepsin

Pancreatin

Rennet

Chlorine. . . . .

1:35614

1:38888

1:7411

1:5980

1:8540

1:27167

-

-

Corrosive sublimate . .

1:65000

1:13000

1:50000

1:17500

1:52000

1:1766

1:21600

1:720

Iodine . . . .

1:5500

1:24070

1:4125

1:1000

1:4166

1:7817

-

-

Hydrochloric acid . . .

-

-

-

-

-

-

Eucalyptus oil . . .

1:100

Acted only in excess

-

-

-

-

-

Bromine . . . .

1:12654

1:28490

1:5070

1:2840

1:5580

1:16777

-

1:31100

Mustard oil . . . .

Only lessens action in saturated solution

-

-

-

-

-

Copper sulphate . . .

1:11000

1:8100

1:6500

-

1:7500

1:110

1:6600

1:200 Has no action

Salicylic acid . . .

1:7600

1:2600

1:5100

1:166

1:1250

1:250

1:9000

1:333 No action

Sulphurous acid . . .

1:21666

1:20485

1:8600 .

1:1940

1:8600

1:1317

-

-

Benzoic acid . . .

1:2100

1:1100

1:1025

1:400

1:2600

1:200

1:2600

1:300

Chloride of lime . . .

1:36713

1:34333

1:6613

1:4950

1:6613

-

-

Has no action 1:28400

Creasote .. . . .

1:60

No action even in saturated solution

1:65

-

-

Thymol . . . . .

1:100

Slight action, or none, even in saturated solution

-

-

-

Carbolic acid . . . .

1:20

1:33

1:30

1:31

1:25

1:50

-

1:100

Borax . . . .

1:100

1:110

1:100

1:3580

1:100

-

-

1:1000

Benzoate of soda . . .

1:100

1:20

1:100

1:65

1:86

-

-

1:50

Turpentine water . . .

1:2

Only weakens

-

-

-

-

-

-

Chloroform . . .

Little or no action, even in saturated solution

-

1:60

-

-

Alcohol . . . .

1:28

1:35

1:3

1:10

-

1:6

1:3

-

Glycerine . . .

1:3

1:2

1:2

1:2

1:3

1:3

-

-

Acetate of aluminium . .

1:50

1:50

Weakens 1:880

Weakens 1:100

Weakens only

-

-

-

Weakens

No action

No action

Weakens

No action

The different action which the same drug exerts upon formed and unformed ferments is of great importance, because upon it depends our power to use the drug in the practice of medicine. Thus creasote, which appears from the preceding table not to destroy the digestive power of ptyalin and to have but a weak action upon that of pepsin, has been found by Werneke to destroy yeast in a dilution of one part to 500 of water; and by Bucholtz to kill bacteria in a dilution of one part to 1,000 of water. This difference enables us to arrest fermentation in the stomach depending on the presence of low organisms, while the digestive action of the pepsin is not interfered with, or only very slightly. The following diagram shows the action of drugs on enzymes and on the lactic ferment, which is a bacillus.

Fig. 14.   Diagram to show the different action of drugs on different enzymes

Fig. 14. - Diagram to show the different action of drugs on different enzymes. The nature of the line showing the action of each drug is shown under its name.