Preserve case in title

I know that I can indicate a foreign language and the case of my title won’t be transformed when cited. But what do I do about a foreign phrase embedded in an English title, when I want the title as a whole to go into title case, but not the foreign section? Can I put it within delimiters of some kind? I tried {}, but it had no effect.

Here’s an example:

The origin and fate of Thomas Bradwardine’s <i>De proportionibus velocitatum in motibus</i> in relation to the history of mathematics

This gets cited (Chicago) as:

“The Origin and Fate of Thomas Bradwardine’s De Proportionibus Velocitatum in Motibus in Relation to the History of Mathematics.”

But it should read:

“The Origin and Fate of Thomas Bradwardine’s De proportionibus velocitatum in motibus in Relation to the History of Mathematics.”

i.e., the Latin title uncapitalized.