Annotations on the back read "Fig 2 to illustrate a paper entitled:- 'Phrenic nucleus of the macaque' insert in text. Remarks-reduce as convenient. 39% to be deleted. Author R. Warwick and G.A.G. Mitchell. Anatomy Dept, University, Manchester 13, England. Compare with accompanying print".
This diagram features, along with VFA.7.339 & VFA.7.341 in the publication R. Warwick & G.A.G. Mitchell, 'The phrenic nucleus of the macaque', Journal of Comparative Neurology, 1956, 105(3), pp.553-85.