The acidity was determined by titration with iV/40 NaOH and using dimethyl-amino-azo-benzene and phenothalein as indicators for the free and the total acidity, respectively. During the 4 years that Mr. V. has been under observation hundreds oi determinations have been made of the acidity of the contents ol the "empty" stomach, of the hunger juice, or continuous secretion, and of pure appetite juice. The reader will recall that the contents of the "empty" stomach are taken one hour after washing out the stomach with 200 c.c. of water. All the cases when the gastric juice or gastric content was contaminated with bil< (intestinal content) are excluded from the summaries given ir Table IV.

The second gastric-fistula case, Mr. E., was a man of twenty-su years of age, healthy and vigorous. Nearly a year prior to oui work on him his esophagus was corroded with a solution of lye and this led to a nearly complete cicatricial stenosis, and hence the gastrostomy. At the time of the observations the esophagus had been dilated sufficiently to permit swallowing of any well-masticated food, and the gastrostomy opening was used only in the dilation processes. In this case, saliva is therefore not excluded from the contents of the empty stomach, and possibly not from the continuous or hunger secretion, although Mr. E. was instructed and urged not to swallow any saliva during these experiments. The appetite juice was obtained by Mr. E.'s chewing palatable food, and spitting out the chewed food, care being taken not to swallow saliva or particles of food.

These results from my two gastric-fistula cases are in agreement with the work of Pavlov and his pupils on dogs, and the work of previous observers on pure gastric juice of normal persons. The latter data have recently been brought together and discussed by Boldyreff.

Table IV. Acidity Of Normal Human Gastric Juice

Normal human gastric juice (appetite secretion) when secreted above a certain minimum rate shows a practically constant total acidity of nearly 0.5 per cent HCl, or the same as the gastric juice of normal dogs. Practically the same figure is obtained when the acidity is determined by conductivity methods (Menten). The gastric juice (appetite as well as hunger juice) secreted by the normal stomach at a low rate shows lower than normal acidity and total chlorides. The view of Pavlov based on experiments on dogs that gastric juice is secreted at uniform and constant acidity is true for man only in regard to appetite, digestion, and hunger juice secreted at fairly high rate. We must take cognizance of the equally important fact that the normal gastric mucosa is capable of secreting a juice of submaximal acidity.

The studies of Rehfus and Hawk on the acidity of the gastric content at varying periods after drinking water and ingesting an Ewald test meal also support the view that the normal gastric juice has a fairly constant acidity.

The reader will note that normal human gastric juice is equal in total acidity to the maximum acidity reported by clinical observeri for so-called hyperacidity in man. So far as we are acquainted with the literature, there is no evidence that the gastric glands under any pathological conditions are able to or do secrete a juice of higher than normal acidity. Actual hyperacidity does not occur in cases oi experimental ulcers in the stomach and duodenum. But there may be hypersecretion. Moreover, the presence in the stomach of gastric juice of full acid strength leads by itself and immediately to no untoward symptoms.

The contents of the "empty" stomach, and the continuous or hunger secretion (when the secretion rate is low) have uniformly a lower acidity than the appetite juice. The total acidity of contents of the "empty" stomach is 0.2 or less. The reader will note that this figure is frequently given as the acidity of pure gastric juice of normal persons. The acidity of the continuous or hunger secretion is higher, and the greater the secretion rate the higher the acidity until it may equal that of the appetite juice. In no instance does the acidity of the continuous secretion exceed that of the appetite juice.

What is the cause of the low acidity of the continuous secretion and contents of the empty stomach ? The following factors must be taken into account:

1. The actual acidity of the juice as secreted may increase with the secretion rate, until the maximum acidity is reached with the high average rate of secretion, under conditions similar to those obtaining in the case of the salivary glands where the concentration of the salts and the organic materials increases with the rate of salivary secretion. If this is a factor the gastric juice secreted at a low rate should show a lower osmotic concentration and a smaller total of chlorides than the juice secreted at high rate. The figures reported by Umber for man and by Rosemann for the dog support this view, the former investigator showing particularly that the osmotic concentration of the gastric juice increases with the rate of secretion. The cryoscopic data may, however, be misleading, as the salts produced by the neutralization of the HCl may not dissociate as freely as the acid.

2. The slower rate of secretion may give a chance for the HCl to be partly neutralized by the alkaline mucus secreted by the mucin cells of the gastric mucosa. This is the factor emphasized by Pavlov. In fact, Pavlov takes the position that in the normal animal gastric juice has practically a constant acidity, irrespective of the secretion rate, but the actual acidity of the juice in the cavity of the stomach is purely a matter of rate of neutralization. If this is the sole factor, the total chlorides of the gastric juice ought to show a greater constancy than the acidity. That the hydrochloric acid of the gastric juice is in part neutralized by the gastric mucus is obvious. But according to Boldyreff the alkalinity of gastric mucus is only 0.05 to 0.10 NaaC03. That is to say, it would require 100 to 200 c.c. of gastric mucus to reduce 100 c.c. of gastric juice from the normal acidity of 0.45 down to 0.25 by neutralization and dilution. The importance of this factor has therefore been overestimated by Pavlov.

3. When the gastric juice is collected from a Pavlov accessory stomach, or from an individual with complete closure of the esophagus, as is the case with Mr. V., the saliva cannot be a factor in lowering the gastric juice acidity by neutralization and dilution. When all or most of the saliva is swallowed the acidity of the gastric juice is necessarily reduced in proportion to the relative rate of salivary and gastric secretion. This is effected by dilution rather than by neutralization, as the titration alkalinity of saliva is low (0.8 Na2C03; Neumeister, cited by Boldyreff).

According to Boldyreff, Carlson, Hicks and Visher, Rehfus and Hawk, an important factor in lowering the acidity of gastric juice from that actually secreted by the gland (0.5) to that usually found in the cavity of the stomach (0.25), is the entrance of the alkaline intestinal contents (pancreatic juice, bile, and succus entericus) into the stomach. This usually occurs, probably, when the acid in the stomach mounts much above 0.25. This "mechanism for self-regulation of the acidity of the stomach content" probably breaks down in cases of so-called "hyperacidity" in man In cases of "hypersecretion" the quantity of juice secreted i greater than normal, and the secretion may persist in the absenc of all normal stimuli, but the neutralizing factors suffice to reduc the acidity of the juice approximately to that found in the norm* stomach. It is purely a balance of secretion rate and of neutralize tion capacity. Impairment of the neutralization factors or a ver excessive secretion rate of gastric juice, or pyloric obstructio would tend to render the acidity of the gastric content equal t that of pure gastric juice; in other words, produce clinical "hypei acidity."