Hydraulic Breather Element

[tomcase580b]

I have a recently purchased late 70's case 580 b. There is a breather element at the hydraulic fill point which was clogged so i purchased a new one and replaced it. i noticed in the parts manual that there is another one on the opposite side of the tractor, yet my tractor has a threaded plug instead.i'm sure the previous owner made this replacement in error. my question is what does the breather element do, and what are the ramifications of not having that second breather element installed.

Thanks in advance for your advise.