My horse, who, under his former rider had hunted the buffalo, seemed as much excited as myself.—Irving.
Other examples might be quoted from Burke, Kingsley, Smollett, Scott, Cooper, Gibbon, and others.
Which.
113. The sentences in Sec. 108 show that—
(1) Which refers to animals, things, or ideas, not persons.
(2) It is not inflected for gender or number.
(3) It is nearly always third person, rarely second (an example of its use as second person is given in sentence 32, p. 96).
(4) It has two case forms,—which for the nominative and objective, whose for the possessive.
Examples of whose, possessive case of which.
114. Grammarians sometimes object to the statement that whose is the possessive of which, saying that the phrase of which should always be used instead; yet a search in literature shows that the possessive form whose is quite common in prose as well as in poetry: for example,—