Thank you to Johannes Bronkhurst, Brendon Gillon, Roland Steiner, Christophe Vielle, Phillip Mass, Adriano Aprigliano who all gave essentially the same answer.

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The "accusative with the infinitive" (Latin: Accusativus cum
infinitivo = ACI) is a special syntactical construction found in
various forms in languages like Latin, Greek and also English. The ACI
forms a subordinate clause to certain verbs. The accusative which is
governed by the main verb ("want" in the example below) is the
"subject" of this subordinate clause with an infinitive as its
predicate. Example in English:

"I want you to do this."

"you" = accusative, "to do" = infinitive.

In German, we have to use another construction:
"Ich möchte, dass Sie das tun." (literally: "I want that you do this.")

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On Tue, Feb 4, 2020 at 11:55 AM Harry Spier <vasishtha.spier@gmail.com> wrote:

Macdonell in his grammar section 211 on the infinitive says:
... It differs from the dative of an ordinary verbal noun solely in governing its object in the accusative. instead of the genetive. .. . . It preserves its original accusative sense inasmuch as it is used as the direct object of verbs. . . .

but then he goes on to say

. . . The construction of the accusative with the infinitive is unknown to Sanskrit, its place being supplied, with verbs of saying, etc., by oration recta with iti . . . .

I'm unclear what he means by "The construction of the acc. with the infinitive is unknown to Sanskrit". when in the first part of this section he describes its its accusative sense and use as the direct object of verbs.

Is he saying that an infinitive can be used as a direct object of verbs except for verbs of saying etc. or something broader?

Thanks,
Harry Spier