The Sale of Goods Act (Ont. s. 4; U. K. s. 2) provides:
4. - (1) Capacity to buy and sell is regulated by the general law concerning capacity to contract, and to transfer and acquire property:
Provided that where necessaries are sold and delivered to an infant or minor or to a person who by reason of mental incapacity or drunkenness is incompetent to contract, he must pay a reasonable price therefor.
Notwithstanding that usually the contract of an infant, lunatic or drunken person is voidable at his option (if in the case of the lunatic or drunken person his state was known to the other contracting party), he may be liable for necessaries.
In the statute the legal liability to pay and the incapacity to contract are put side by side as co-existent, and the infant or other person who is incompetent to contract would seem to be liable for necessaries, not because he is in this respect able to contract, but because he is bound quasi ex contractu.
Anson, Contract, 15th ed. 1920, pp. 141-2; Nash v. In-man,  2 K.B. 1, at p. 8.
The statutory definition of necessaries states the result of many decisions. The English cases are collected in Benjamin, Sale, 5th ed. 1906, pp. 46 ff., and 17 Halsbury, Laws of England, pp. 67-69, 25 Halsbury, op. cit., pp. 124, 125.
In Roberts v. Gray,  1 K.B. 520, it was decided that a contract by an infant for necessaries and for his benefit is binding on him,and cannot be repudiated by him on the ground that it is partly executory. At pp. 525-6, Cozens-Hardy M.R. said:
We have had our attention called to a great number of cases dealing with the circumstances under which and the extent to which an infant may be bound by, and be incapable of repudiating, a contract made by him during infancy. Far be it from me to say that there has not been some development of the law since the age when the earliest cases which have been cited were decided, but it is important to remember that as early as Coke - Co. Litt. 172 A - it has been held that an infant's contract for necessaries is binding, and it was laid down by him that that doctrine also applied not merely to bread and cheese and clothes, but to education and instruction.
An infant cannot be sued on a negotiable instrument or a bond with a penalty, even though given for the price of necessaries, but he may be sued for the reasonable price of the necessaries, and apparently he may be sued on a bond without a penalty given for necessaries, the claim being treated as one upon a simple contract.
In re Soltykoff,  1 Q.B. 413; Walter v. Everard,  2 Q.B. 369; Beam v. Beatty, 1902, 4 O.L.R. 554.
A person maintaining a lunatic is entitled to recoupment from the estate of the lunatic, having regard to the position in life of the lunatic. A person who lends, to the person maintaining the lunatic, money which is applied in the provision of necessaries for the maintenance of the lunatic, is entitled to be subrogated to the position of creditors for such necessaries who have received payment out of the money advanced. In re Beavan,  1 Ch. 196.