2. Aqueous solution of methyl-violet (an aniline dye) in the strength of 0.025 per cent. (Witz, Maly). The solution should be of a violet color, and in a test-tube should allow the light to pass readily through it. The addition of hydrochloric acid in dilute solution changes the violet to a blue color, in stronger solution to a greenish tint. With lactic acid in stronger solution methyl-violet gives a similar but less distinct reaction. Methyl-violet, while a less delicate test than tropæolin, is better adapted for distinguishing hydrochloric from lactic acid.
3. Ferric chloride and carbolic acid test (Uffelmann). Mix 3 drops of liquor ferri chloridi (German Pharmacopoeia, specific gravity 1482), 3 drops of very concentrated solution of carbolic acid, and 20 ccm. of distilled water. The addition of even very dilute solutions of lactic acid (0.05 per cent.) changes the amethyst-blue color of this test-fluid to a yellow color, with a shade of green. Dilute solutions of hydrochloric acid produce a steel-gray, and stronger solutions a complete decolorization of the fluid. When both hydrochloric and lactic acids are present the effect of the lactic acid predominates unless only a mere trace of it is present. This is therefore a good test for lactic acid. It is necessary to prepare the test-fluid fresh each time before using.
4. It is well to test the digestive power of the filtered fluid from the stomach by suspending in the fluid a floccule of washed fibrin and keeping the fluid at a temperature of about 100° F. If free hydrochloric acid be present in moderate quantity, in a short time the fibrin will begin to be dissolved, but if the acidity be due to organic acid the fibrin will be dissolved very slowly or not at all.
In applying these various tests the fluids from the stomach should be filtered and the filtrate used. It is best not to rely upon a single test, but to employ them in combination. The fluids may be mixed in a test-tube. The reaction is sometimes most distinct when the fluids are allowed to mingle upon a white porcelain dish. It is sometimes of advantage to concentrate the mingled fluids by evaporation. The fluid obtained by the stomach-pump five or six hours after a meal is the most suitable for diagnostic tests. The presence of peptones and of dissolved albumen makes the tests less delicate for the gastric fluids than for simple aqueous solutions of the acids.44
44 For further information on this subject consult Von der Velden, loc. cit.; Uffelmann, Deutsches Arch. f. klin. Med., Bd. 26, p. 431; Edinger, ibid., Bd. 29, p. 555; and Kredel, loc. cit.
It is important to distinguish between the slight and the copious hemorrhages of gastric cancer.
The admixture of a small quantity of blood with the vomit, giving to the latter the so-called coffee-grounds appearance, is a very common occurrence in gastric cancer. Melænamesis, as the vomiting of brown or black substance resembling coffee-grounds is called, is estimated to occur in about one-half of the cases of cancer of the stomach. It is observed particularly in the cachectic stage, in which it is not rare for some brown or black sediment to be almost constantly present in the vomit. The brown or black color is due to the conversion by the acids of the stomach of the normal blood-coloring matter into dark-brown hæmatin.
The presence of blood in the vomited matter can generally be recognized by the naked eye. By the aid of the microscope red blood-corpuscles, more or less changed, especially decolorized red blood-corpuscles (the so-called shadows), can usually be detected. Sometimes only amorphous masses of altered blood-pigment can be seen. The spectroscope may also be employed, in which alkaline solutions of hæmatin produce an absorption-band between C and D, usually reaching or passing D. The presence of blood-coloring matter can also be readily detected by the production of hæmin crystals.45 The slight hemorrhages are in most cases the result of ulceration of the cancer, by which process a little oozing of blood from the capillaries is produced.
45 Hæmin crystals may be produced by boiling in a test-tube a little of the suspected fluid or sediment with an excess of glacial acetic acid and a few particles of common salt. After cooling, a drop from the lower layers will show under the microscope the dark-brown rhombic crystals of hæmin in case blood-coloring matter was present in not too minute quantity.
Copious hemorrhages from the stomach are not common in gastric cancer. They occur probably in not over 12 per cent. of the cases (Lebert). According to Lebert, they are more liable to occur in males than in females. Blood vomited in large quantity is either bright red or more or less darkened in color according to the length of its sojourn in the stomach. Following profuse hæmatemesis, some dark, tarry blood is usually passed by the stools, constituting the symptom called melæna. Copious hemorrhages from the stomach hasten the fatal termination and may be its immediate forerunner. Cases of gastric cancer have been reported in which death has occurred from gastrorrhagia before there has been time for any blood to be either vomited or voided by stool. As might naturally be expected, patients with gastric cancer do not usually rally as readily from the effects of gastric hemorrhage as do most patients with simple ulcer. Profuse gastric hemorrhage, if it occur, is most common in the late stage of gastric cancer, but I have known a case of cancer of the stomach in which copious hæmatemesis was the first symptom, with the exception of slight dyspepsia.46