'Stephen Jacyna relates the ways in which Sherrington's long-term correspondent, the also physiologically-educated Henry Head, began to formulate a conception of sensory experience in which all parts of the nervous system became active contributors to, rather than (as in associationist models) passive conveyors of, sensations. Head's studies centred on clinical testing and self-experimentation rather than laboratory precision (Jacyna 2008, esp. 125-131 and 144-151). [note: 'On the subsequent emergence of a medical 'neurology' see Casper 2014, esp. pp. 84-95.']'