GASTRIC FERMENTS.

By DR. C. F. MENNINGER, Topeka.

AS FAR back as the beginning of the sixteenth century the

phenomena of digestion claimed much attention from students. There was no little diversity of opinion as to how the food was digested. Some held that it was done by pure. mechanical action of the stomach, and others explained digestion as due to a dissolving and transforming activity of the juices of the stomach.

Reaumur, who lived from 1683 to 1757, advocated that digestion of food was due to the action of the juices of the stomach. He demonstrated this by causing animals to swallow metallic perforated capsules filled with food. After these had been cast out he examined the contents of the capsules and found that certain substances had been dissolved out while others had not thus been affected. Somewhat later, Spallanzani devoted himself to the investigation of the juice of the stomach and arrived at positive knowledge as to the cause of food digestion in the stomach. He did this by causing birds to swallow small sponges which by means of a string he withdrew, after some delay. In this way he obtained gastric juice and made the first recorded artificial digestion in vitro.

For 100 years these conclusive scientific experiments were buried under an avalanche of scientific (?) theories and rubbish, and not until the masterly works of Kirchoff, Eberle, Schwann, Schönbein, Pasteur and Dubrunfaut, within the memory of living man to-day, has science been injected into the study of the ferments.

Ferments were formerly classified into true ferments, this term being applied to bacteria, molds, etc., which caused the decomposition of an organic substance, and false ferments, these being the soluble enzymes of the bacteria, molds, etc. To-day we know, however, that living molds act because they contain the ferment, and the true agent in every case of fermentation is the soluble enzyme, and also that the enzyme wil! act after the death of the parent cell.

Ferments are also divided by some quite modern investi

gators into organic and inorganic. The organic ferments are those catalytic agents produced in living cells or tissues or produced by the processes of nutrition of low organisms, which have the property of accelerating the decomposition of complex unstable compounds into simpler substances. The inorganic ferments are those catalytic agents of the mineral world composed of colloidal solutions of the nobler metals, as platinum, silver, iridium, gold, which have the property of accelerating the chemical reactions of two different substances. Here also we deal with chemical reactions which take place even when no ferments are present. Thus far no objection can be safely and permanently maintained against this classification, but to divide the former class, namely, the organic ferments, into two classes or groups, the so-called organized and unorganized, cannot be successfully accomplished. The term organized ferments is applied to those which are connected in some way with the life of the cells in which they are produced and which cannot be extracted from these cells. The unorganized ferments, commonly called enzymes, can, on the other hand, be extracted from the cells in which they are formed, and are able to produce their characteristic actions outside of the cells as well. Those who hold to this classification of organized and unorganized organic ferments, the enzymes, admit that the list of the unorganized ferments is constantly growing at the expense of the organized; that as soon as we will be able to successfully extract the organized from the living cell we will speak of unorganized ferments or enzymes alone. Buchner's successful extraction of zymase from the yeast-cell, which is able to bring about the decomposition of glucose into alcohol and carbon dioxid quite as readily as the yeast-cell itself, is a grand demonstration of the certainty of the coming of such events. Ferments play a most important part in the phenomena of assimilation and of disassimilation of foods. Most of the foods which occur in nature at the disposition of men, lower animals or plants, are not directly assimilable; they require the intervention of a ferment in order to be transformed into substances assimilable and suitable for the formation of new tissues. Pepsin is one of the oldest, if not the oldest, and most thoroughly well known ferment. It was so named by Schwann in 1835, fifty-six years after Spallanzani had shown that the gastric juice can produce chemical changes outside of the body. This

ferment, called under the newer nomenclature acid-proteinase, because it acts in acid medium upon protein, gelatin and connective tissues, is present in the stomach of the human being from the time of birth. It is secreted in the fundic, as well as in the pyloric portions of the stomach. Formerly it was quite generally thought that the parietal (delamorphic, oxyntic) cells were the pepsin cells, but since the investigation of Heidenhain and his pupils, Langley, and others, the formation of pepsin has been shifted to the chief cells (adelomorphic, principal of central). Pepsin occurs in the mucous membrane only in the preliminary form of its zymogen, pepsinogen. Pepsin is destroyed by soda. If, however, the mucous membrane be extracted with a weak soda solution and the extract be then acidified with HCl, a pepsin-containing fluid of good digestive properties is obtained. (Langley.) Therefore, there must be in the mucosa a substance which is not destroyed by soda, and which is transformed into pepsin by treatment with acids.

From pure gastric juice of the dog, Nencki and Sieber, also Pekelharing, have prepared by dialysis and precipitation a very pure pepsin. Pekelharing claims to have prepared the purest acid-proteinase thus far obtained, and classes the enzyme among the proteins. His preparation gives the wellknown reactions for protein, and on analysis shows the presence of carbon, nitrogen, hydrogen and sulfur in the proportions in which they exist in proteins. It contains no phosphorus, hence is no nucleo-proteid. Chlorin was found to be a constant constituent. Pekelharing's preparation is the most active preparation of this ferment obtained thus far, 0.001 milligram in 6 cc. of a 0.2 per cent. HCl solution dissolved a flake of fibrin in a few hours.

Pepsin splits the proteins into a number of different substances. The farther the cleavage proceeds the simpler will the composition of these substances be. These substances may be separated one from another by fractional precipitation with ammonium sulfate.

The nature of the products formed by this cleavage have been very thoroughly investigated within the past few years. Where we once believed that proteoses and peptones constituted the final products of gastric digestion, ready for absorption and assimilation, we now know that a large number of substances which were formerly looked upon as produced

only in pancreatic digestion are also formed. The same substances as those formed in the action of tryptic digestion on protein are formed in gastric digestion, and in consequence we now look upon and ascribe to the gastric juice much greater digestive importance, so far as the proteins are concerned, than heretofore.

Caseinase, rennin, rennet, lab-ferment, are names given to the other important ferment found in the stomach which has the power of curdling milk.

The pepsin of Pekelharing, the purest and most potent ever extracted, is able not only to act on proteins but also curdles milk. Pepsin and rennin seem to be therefore parts of the same molecule. This view was suggested by Nencki and Sieber before him. A number of authors have pointed out the fact that rennin always coexists with a proteolytic ferment. In the human being and in certain other animals rennin accompanies the pepsin of the stomach and the trypsin of the pancreas. Rennin also is found in largest amounts in those portions of the stomach where the most pepsin is found, namely, the fundus.

COMPOSITION OF GAS FROM COTTONWOOD TREES. By F. W. BUSHONG.

BOUT ten years ago, while cutting down some cottonwood

trees, the writer observed the formation of bubbles in the sap upon the freshly cut trunk, stump and chips. On applying a lighted match the gas emitted proved to be combustible. In the latter part of July, 1907, gas was collected from a cottonwood tree in the following manner:

An inch hole was bored into the trunk to the heart. A piece of gas-pipe provided with a stopcock was screwed tightly into this hole. A rubber tube conveyed the gas from the stopcock to a bottle previously filled with distilled water and inverted in a dish of distilled water. Two bottles of gas, about four liters, were collected and used for preliminary experiments, but were not used for analysis because they contained the air originally in the gas-pipe, etc. A third bottle of gas was reserved for the analysis, which was made November 27, 1907, with the following average results from two complete and two partial analyses by Professor McFarland: