(d) The assimilation limit, that is to say, the limit up to which the in-take of sugar must be raised in order that the urine may be come saccharine, varies according to the different kinds of sugar. Sugar appears in the urine after a simple ingestion of : The figures given refer to the amounts taken when the individual is fasting; when the stomach contains food the assimilation limit is higher. It is to be understood that these figures are only approxi mate, for there are considerable variations in the assimilation limits in different individuals.
(e) A positive reaction to the sugar test appears ordinarily in from three-quarters of an hour to an hour after the ingestion of a single large dose, and continues for from one to three hours. The total amount excreted equals, in the case of cane sugar about 2.8 per cent. of the amount taken, of grape sugar 1 per cent., and of milk sugar 0.8 per cent.
(1) The assimilation limit for starch is unattainable, that is to say, starch may be taken in any amount without resulting in an ex cretion of carbohydrates in the urine. Evidently in this case diges tion and absorption consume so much time that a sudden flooding of the blood with carbohydrates cannot take place. This is a fact of much importance, for it signifies that those who excrete sugar after the ingestion of starch have a morbidly depressed assimilation limit, and the existence of diabetes mellitus is to be strongly suspected.
4. Paoperal Lactosuria.'—In the same line with alimentary gly cosuria is to be placed puerperal lactosuria. This condition was dis covered by Blot in 1850, and later (1877) F. Hofmeister and Kalten bach showed that the excreted substance was Milk sugar. Since that time the term puerperal glycosuria has been abandoned, puerperal lactosuria being employed in its stead. The theory was at once ad vanced that this lactosuria owed its origin to a process of resorption in the mammary glands, the milk sugar formed in the breasts being taken up with the milk by the blood and excreted unchanged by the kidneys. Further investigations have shown that the affection is encountered when there is an interruption to the withdrawal of milk, as when, because of excoriation of the nipple, a nursing woman has to refuse the breast to the child, or when the infant cannot nurse prop erly. When, despite an abundant withdrawal of milk, lactosuria is
present, the fault lies in a liypersecretion; the affection is observed occasionally in women who secrete such an abundance of milk that they could easily nurse two children instead of one. The sugar gen erally appears in the urine at the time when a more profuse secretion of milk begins, that is, on the second, third, or fourth day of lacta tion, and disappears gradually as the child increases the size of its meals.
So far for known facts. That a gland secretion in excess of the needs of the organism may be taken up into the circulation and, in part at least, excreted in the urine, is not without analogy in the organism. I may recall, as an example, the fact that, in an individ ual who is fasting and, in consequence of insu flicient stimulation of the peripheral nerves, secreting but little saliva, a very appreciable quantity of the salivary ferment (ptyalin) is resorbed and passes out in the urine. The same is true of the waste products of metabolism when, in consequence of obstruction to their outflow, they are thrown back into the circulation (bile pigments and biliary acids). The latter are excrementitious substances and must be removed from the organism under penalty of producing toxic symptoms. In the•ease of milk sugar the question is different. We have here to do with a substance which is in an eminent degree a physiological nutrient ma terial, a substance which is taken in " milk-cures" to the amount of 100 to 150 grams a day, and which can be ingested by most healthy individuals in single doses of 100 grams and be rapidly absorbed without a trace escaping decomposition and appearing in the urine. Why then should a nursing woman excrete in the urine the certainly very small amount of sugar which she has elaborated in her own mammary glands and which has been thence taken up into the blood? A number of researches which I have made with a view to a solution of this problem have led me to the hypothesis that, in the puerperal state, the capacity of the tissues for breaking up milk sugar is diminished. We have here an instance of adaptation to an end, in that the cells of the mother refuse a material which is pre eminently suited to the nutritive wants of the nursling.