likely to become a habit, and stick to him for years--until, indeed,
he become a big boy_?

After he have cut the whole of his first set of teeth, that is to say,
when he is about two years and a half old, he might, if it be likely
to become a habit, be readily cured by the following method, namely,
by making a paste of aloes and water, and smearing it upon his
thumb. One or two dressings will suffice as after just tasting the
bitter aloes he will take a disgust to his former enjoyment, and the
habit will at once be broken.

Many persons I know have an objection to children sucking their
thumbs, as for instance,--

"Perhaps it's as well to keep children from plums,
And from pears in the season, and sucking their thumbs." [Footnote:
_Ingoldsby Legends_.]

My reply is,--

P'rhaps 'tis as well to keep children from pears;
The pain they might cause, is oft follow'd by tears;
'Tis certainly well to keep them from plums;
But certainly not from sucking their thumbs!
If a babe suck his thumb
'Tis an ease to his gum;
A comfort; a boon; a calmer of grief;
A friend in his need--affording relief;
A solace; a good; a soother of pain;
A composer to sleep; a charm; and a gain.