With the optical resolution of trans- (“normal”) αγ-dimethylglutaconic acid by McCombs, Packer and Thorpe (J.C.S. (1931) 134 547 – a reprint of this paper is attached) the question as to whether this compound should be represented as having a “normal” form (I) as has been held by Thorpe, or the conventional formula (II), was settled in favour of the latter. [Diagram] Since the “normal” formula is essentially symmetrical, the formula (II) (trans- configuration) is the only one on which all the properties of the acid may be explained.