“ Trephining has been considered as indicated when there is a fracture of a portion of the skull, from a fall or blow with a blunt instrument, in order to elevate the depressed portion; in some cases of concussion, where there is reason to believe that the inner table of the skull is fractured at the opposite side of the head, and is producing irritation of the brain ”

“ A sharp steel point called a centre pin, which can be pressed into the bone until the saw has made a groove for itself, passes down the centre of the instrument, and is removable by the operator as soon as the groove is made. ”