During the first week or two, exclusive milk diet gives rise to a marked sense of sleepiness. It causes nearly always, and even for weeks of its use, a white and thick fur on the tongue, and often for a time an unpleasant sweetish taste in the early morning, neither of which need be regarded. Intense constipation and yellowish stools of a peculiar odor are usual. Of the former I shall speak in connection with the use of milk in special cases. The influence of milk on the urinary secretion is more remarkable, and has not been as yet fully studied.
There is, of course, a large flow of urine; and in dropsical cases due to renal maladies this may exceed the ingested fluid and carry away very rapidly the dropsical accumulations. It is sometimes annoying to nervous persons because of the frequent micturition it makes necessary. I have discovered that while skimmed milk alone is being taken, uric acid usually disappears almost entirely from the urine, so that it is difficult to discover even a trace of this substance; nor does it seem to return so long as nothing but creamless milk is used. Almost any large addition of other food, but especially of meat, enables us to find it again. Creatine and creatinine also seem to lessen in amount, but of the extent of this change I am not as yet fully informed.
A yet more singular alteration occurs as to the pigments. If after a fortnight or less of exclusive milk diet we fill with the urine a long test-tube, and, placing it beside a similar tube of the ordinary urine of an adult, look down into the two tubes, we shall observe that the milk urine has a singular greenish tint, which once seen cannot again be mistaken. If we put some of this urine in a test-tube carefully upon hot nitric acid, there is noticed none of the usual brown hue of oxidized pigment at the plane of contact. In fact, it is often difficult to see where the two fluids meet.
The precise nature of this greenish-yellow pigment has not, I believe, been made out; but it seems clear that during a diet of milk the ordinary pigments of the urine disappear or are singularly modified. A single meal of meat will at once cause their return for a time.
These results have been carefully re-examined at my request by Dr. Marshall in the Laboratory of the University of Pennsylvania, and his results and my own have been found to accord; while he has also discovered that during the use of milk the substances which give rise to the ordinary fæcal odors disappear, and are replaced by others the nature of which is not as yet fully comprehended. The changes I have here pointed out are remarkable indications of the vast alterations in assimilation and in the destruction of tissues which seem to take place under the influence of this peculiar diet. Some of them may account for its undoubted value in lithæmic or gouty states; but, at all events, they point to the need for a more exhaustive study both of this and of other methods of exclusive diet.