1941, George C. Booth, Mexicos School-made Society'', page 106
There are four fundamental figures. One is a man measuring and comparing his world(..) In front of him is a macabre figure, a cadaver ready to be dissected. This symbolizes man serving mankind. The third figure is the scientist, the man who makes use of the information gathered in the first two fields of mensurable science.
1993, Theodore Ziolkowski, "Wagner's Parsifal between Mystery and Mummery", in Werner Sollors (ed.), The Return of Thematic Criticism, pages 274-275
Indeed, in the 1854 draft of Tristan he planned to have Parzival visit the dying knight, and both operas display the same macabre obsession with bloody gore and festering wounds.
The appeal of the spectrally macabre is generally narrow because it demands from the reader a certain degree of imagination and a capacity for detachment from every-day life.