Sentence:  Because of a:— counterbalancing relationship between <WSD>onbeam</WSD> excitation and inhibition at the Purkinje cell (Eccles et al., 1967) some manner of continually refurbished excitation from these extramuscular receptors must be postulated (Murphy, MacKay & Johnson, 1973) 
Meaning of the word marked with <WSD> tags:  In line with excited parallel neurofibers.