Complex sentence: Among other pieces ne on his teeth, which seemed to drop out at regular intervals, so that he could calculate roughly what span of loetry cannot be classed with that of the highest order, unlike his prose writings.
Split into simpler sentences: Among other pieces there is one on his teeth, which seemed to drop out at regular intervals, so that he could calculate roughly what span of life remained to him. Altogether, his poetry cannot be classed with that of the highest order, unlike his prose writings.