William Alcott - The Young Mother - Management of Children in Regard to Health

Oxygen gas is the chief supporter of combustion, as well as of respiration. It is the vital part, as it were, of the air. No animal or vegetable could long exist without it. And yet if alone, unmixed, it is too pure and too refined for animals to breathe. Nitrogen gas, on the contrary, while alone, will not support either respiration or combustion; mixed, however, with oxygen, it dilutes it, and in the most happy manner fits it for reception into the lungs.

I say, from early infancy; because we may adopt the best habits in mature years, after our constitutions have been broken up by error and vice, without effecting anything more than to keep us from actually sinking at once. Indeed, in most cases we ought not to expect more.

Nothing is intended to be said here, which shall encourage unthinking nurses or mothers in setting themselves against measures which have been prescribed by higher authority,—I mean the physician. There are cases of this kind, where it requires all the resolution which a father, uninterrupted, can summon to his aid, to administer a dose or perform a task, on which he knows the existence of his child may be depending: but when the thoughtless entreaties of the mother or nurse are interposed, it makes his condition most distressing. Mothers, in such cases, ought to encourage rather than remonstrate. They who do not , are guilty of cruelty, and—perhaps—of infanticide.

"Dewees on children" p. 72.