Corporal Herbert Edward (“Doctor”) Rockall
“One night about this time a party of us, including Hunt and ‘Doctor’ Rockall, the medical corporal, who had accompanied me round the front posts, lost its way hopelessly in the dark.”
“On our way to reach Fry we were both knocked down in the trench by a 4.2, which also wounded Corporal Rockall in the shoulder-blade.”
I’m 99% sure that it is Herbert E. Rockall mentioned above. As the document below gives details of him being wounded in action on 24th February 1917.