midnight
He had hardly done so , when the policeman -- a burly man well over six feet in height , who was standing bolt upright as if at `` attention , '' his limbs absolutely rigid , his eyes wide open and expressionless -- began to speak in a soft , lisping voice that the trio at once identified with the voice of the Unknown -- the voice of the tree on that eventful night in San Francisco . `` The great secret of medicine -- the secret of healing -- will now be revealed to you , '' the voice said . `` Pay heed . In cases of tumours and ulcers take a young seringa , lay it for half an hour over the stomach of the afflicted person , then plant it with the mumia , _ i.e. _ either the hair , blood , or spittle of the sick person , at midnight . As soon as the seringa begins to rot , the ulcer will heal . `` In phthisis pulmonalis , the mumia of the sick person should be planted with a cutting of the catalpa , after the latter has been subjected for some minutes to the breath of the diseased person . As soon as the cutting shows signs of decay , the sick person will be cured .