The recurrence, moreover, of pregnancy in the lactescent female may render the milk of a bad quality, and will invariably lessen its quantity. Mr. Burns asserts that in these cases the milk 'does not become hurtful,' but in this opinion I must beg leave to differ from him; since I have repeatedly seen it, from this cause, palpably altered in appearance, and have observed diarrhœa and great debility produced in the children who were suckled with it. An almost universally received opinion among females, and, indeed, one very frequently entertained by members of the medical profession, is, that while a woman continues to nurse her infant she will not again become pregnant; but this, as a general proposition, is unquestionably erroneous; it is even doubtful whether such opinion will hold good in a majority of instances. The continuance of lactation will very generally, it is true, tend to prevent the recurrence of the periodical phenomenon; yet, nevertheless, it will not in every instance prevent pregnancy[B]. Should, however, a woman with an infant at the breast again become pregnant, (a circumstance that very frequently occurs, and of which, from the _general though not invariable_ absence of those criteria by which this fact is accustomed to be recognised, she is not aware until it has made some progress,) one of two things will usually take place; either she will miscarry, or her milk will become impoverished in quality and diminished in quantity. Nor is this wonderful:--it was not intended by Nature that the processes of pregnancy and lactation should go on simultaneously, but, on the contrary, that the one should commence when the other had terminated; and experience sufficiently proves that they will not proceed well together: the reason of which, as it appears to me, may be easily given. During pregnancy, and particularly during its latter periods, the vessels of the womb gradually enlarge, and a much greater quantity of blood than usual is determined to that organ for the increase and perfection of the embryo and its appendages; which, after delivery, becomes transferred to the breasts to supply the material for the secretion of the milk: but if, during pregnancy, lactation be also persevered in, the blood becomes directed at the same time to two different parts of the body, somewhat remote from each other, namely, to the womb, and to the breasts; hence, neither is likely to receive its due proportion of this vital fluid, and, consequently, the functions of one or the other, or both, are liable to become impeded or suspended. If the breasts continue to receive a sufficient quantity of blood, the secretion of milk goes on properly, but the womb is deprived of its necessary supply; the embryo, in consequence, languishes and dies, and, becoming an extraneous body, is thrown off, producing abortion; while, on the other hand, should the womb still obtain its due proportion of blood, the breasts are robbed of it, and the secretion of