a. rare. [f. med.L. summāt- (see SUMMATE) + -IVE.] Operating by means of addition; additive.
1881. G. S. Hall, German Culture, 235. Relatively large and strongly-acting motor cells, whose connections with each other are mainly summative.
1891. G. S. Woodhead, Bacteria, 379. Both the antagonistic action and this summative action.
