the veins and nerves from the head (see Molina)
quatlalhuayotl. las venas, o neruios dela cabeza. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 86r. col. 1. Thanks to Joe Campbell for providing the transcription.