Sentence:  The two last, the "intertransversarii" and "quadrati lumborum", are here enumerated with the dorsal <WSD>inflectors</WSD>, because the are dorsad of the centre of motion, and accordingly relaxed in the dead body, when the trunk is inflected in the dorsal direction. 
Meaning of the word marked with <WSD> tags:  A muscle that contracts to cause a part of the body to curve inwards.