Mrs. A----, a lady of delicate constitution, about twenty years of age, three or four months subsequent to the birth of her first child, began to find her milk gradually lessen in quantity; it had also much changed from its previous appearance, resembling at the time just stated, a yellowish, turbid serum. Her child became emaciated; and diarrhœa supervening, my professional services were required. My advice was, that the child should be at once weaned, and a suitable wet-nurse, if possible, procured--neither of which suggestions, as will shortly appear, were followed. I urged the necessity of this measure more particularly, because Mrs. A---- was daily getting thinner and weaker; she also complained of great pain in the head and back, and of an increasing dimness of sight, which made her fear she should become blind; but the mother-in-law of my patient being, unfortunately, of opinion that pregnancy in the latter would not again occur during the continuance of lactation, recommended that the child, although chiefly supported upon spoon-meat, should occasionally be allowed to take the breast; and this plan, notwithstanding the wish of Mrs. A---- to the contrary, and my own remonstrances on the subject, was adopted--the effects of which were to increase the mother's ailments, as well as those of her infant. Things went on thus for some time longer, when I once more endeavoured to persuade Mrs. A---- to follow my advice, observing, that by an opposite line of conduct she was not only injuring her own health, but that of her child, neither of which, I assured her, in my opinion, would be re-established till the latter had been weaned. I expressed also my complete incredulity as to the non-recurrence of pregnancy in consequence of her infant remaining at the breast; and I added--'It is my firm conviction that if you be pregnant, or should happen shortly to become so, you will miscarry.' About a week after this conversation she was suddenly seized with flooding, and what I had predicted took place. She now left off suckling, and in about a month, under suitable treatment, completely got rid of all her former complaints: the child also immediately began to improve. The present case clearly proves that the process of lactation will not _invariably_ prevent the occurrence of pregnancy, since Mrs. A---- became in this state, notwithstanding she continued to suckle her child: and I think few will be so hardy as to doubt that it was the cause of her miscarrying: more particularly when I mention that, at a future period, the same lady, during my absence abroad, being once more persuaded to try whether she could not avoid becoming pregnant (which was very much to be desired, on account of her delicate state of health) by continuing to perform the duties of a nurse, again suffered all the distressing symptoms before described, and again miscarried.