The quotation is from Horace, Satires, I, 2, starting at line 111
The grammar in this passage is difficult for me, with respect to the future participles, and with respect to the usage of quem and quid.
nonne, cupidinibus statuat natura modum quem,
quid latura sibi, quid sit dolitura negatum,
quaerere plus prodest et inane abscindere soldo?
nonne . . . plus prodest quaerere: is it not more profitable to inquire
modum quem: what limit cupidinibus statuat natura: nature sets to desires quid latura sibi: what she might [properly] receive. I suggest latura=latura sit. quid sit dolitura negatum: what thing denied might she suffer from
I suggest that latura and dolitura, being active participles, agree with natura.
et inane abscindere soldo: and separate the real from the empty.
quaerere . . . abscindere: these are parallel infinitive complements of _prodes_t, I believe.
cupidinibus statuat natura modum quem. The quem is severely displaced to the end of the clause it introduces(!). “(Is it not more profitable to inquire) what measure/limit Nature sets on desires?” statuat subjunctive in indirect question.
quid latura sibi, quid sit dolitura negatum. sit and negatum each apply to both clauses: “what she’ll put up with (and) what she’ll grieve over (if it were) denied her.” i.e. how much privation she can stand before she really begins to suffer. Going without luxury goods, as distinct from basic necessities, is tolerable.
This meaning of fero, “bear” in the sense of “tolerate” or “put up with,” is quite common.
I take sibi not with latura but with negatum, lit. “what, denied her, would she …”—applying to both halves of the line. You can understand the participle (sibi) negatum, agreeing with each quid (acc.), as having conditional force. sibi negatum “(if) denied to her,” sibi reflexive.
These are indirect questions too, clarifying the previous one.
The future has no subjunctive forms of its own, so fut.subj. is always periphrastic: future participle + appropriate form of sum. (It can be used in indicative too: feram I shall bear vs. laturus sum I am about to bear.) swtwentyman had a thread on the future periphrastic a little while back, http://discourse.textkit.com/t/future-periphrastic/14435/1 but you probably don’t need that. sit subjunctive here because indirect, same as statuat in previous line.
inane abscindere soldo to separate (sever, cut away) the insubstantial (i.e. what’s unnecessary by nature’s standards) from the solid—like a sculptor chiselling away what’s superfluous. inane of course implies vain.
The corrections by mwh, for which I thank him, dealt with all the problems I raised, except the matter of quem and quid. I’ll attempt a homemade explanation, citing the Allen and Greenough. This is a topic on which I needed review.
In the first line quoted above, quem is an Adjective Interrogative Pronoun, modifying modum. This pronoun form is declined just like the relative pronoun, qui, quae, quod. (A&G, #148b)
The two instances of quid, both in the middle line a both examples of the Substantive Interrogative Pronoun, quis, quis, quid. (A&G, #148)
Yes that’s right. You showed in your original post that you understood how quem and quid were being used, so it wasn’t clear what “problem” you had with them.
The fact that they introduce (indirect) questions (as I said) means they’re “interrogative.”
quem is here “adjectival” on account of modum, while the repeated quid is “substantival” inasmuch as it stands independently, functioning like a noun. You showed you understood that.
Also: quem is masculine as agreeing with modum, and quid is neuter (and negatum agrees with it). And they’re all accusative, quem modum the direct object of statuat, the two quids the direct objects of latura (sit) and sit dolitura respectively. All this too you seemed to show you understood. In my post I tried to cover points that you may not have understood correctly.