Drawings, white and grey substance from calf spinal chord by J [Jacob Augustus] L [Lockhart] Clarke Plate 20, figures 1-3 showing sections of the white and grey substance found in the spinal chord of a calf. Inscribed with publication and plate details. Faint outline drawings of the figures visible verso. Signed in ink bottom left 'J. L. Clarke ad nat delt.' Subject: Anatomy Published in Philosophical Transactions as part of paper titled 'Researches into the structure of the spinal chord' by Jacob Augustus Lockhart Clarke. Received by the Royal Society on 15 October 1850. Read 5 December 1850. [1850]