“…The first of these ques tions had already been thoroughly investigated (see reviews by Bollard and Butler, 1966;O'Kelley, 1968) and it seemed that the elements required in major quantities (apart from carbon, hydrogen and oxygen) were nitrogen, phosphorus, calcium, magnesium, potassium, sulphur, iron and perhaps chlorine (Greenfield, 1942;Myers, 1951;Tamiya et al, 1953;Walker, 1953;Knauss and Porter, 1954). Elements required only in trace amounts included boron, cobalt (Greenfield, 1942), man ganese, copper, molybdenum, zinc (Walker, 1953;1954) and vanadium (O'Kelley, 1968). There appeared to be some doubt over the possible requirement for sodium (O'Kelley, 1968).…”