While there is doubtless a recognized standard of normal perception, yet the acuteness with which sensations are perceived by different individuals, even in ordinary health, passes through a wide scale of variation, both above and below this standard. The difference in the ability to see and recognize natural objects, signs, and indications, between the ordinary city denizen and, for instance, the American Indian or the white frontiersman, hunter, or scout, is something marvellous.
So, also, regarding the power to distinguish colors. One person may not be able to distinguish even the simple or primary colors, as, for example, red from blue or green, while the weavers of Central or Eastern Asia distinguish with certainty two hundred or three hundred shades which are entirely undistinguishable to ordinary Western eyes.
So of sound. One ear can hardly be said to make any distinction whatever regarding pitch, while to another the slightest variation is perfectly perceptible. Some even do not hear at all sounds above or below a certain pitch; some persons of ordinary hearing within a certain range of pitch, nevertheless, have never heard the song of the canary bird, and perhaps have lived through a large portion of their lives without even knowing that it was a song-bird at all. Its song was above the range of their hearing. Some never hear the sound of the piccolo, or octave flute, while others miss entirely the lowest notes of the organ.
There is the same great difference in perception by touch, taste, and smell. In certain conditions of disease, accompanied by great depression of the vital forces, this deviation from normal perception is greatly increased. I have had a patient who presented the following briefly-outlined phenomena:—
After a long illness, during which other interesting psychical phenomena were manifested, as convalescence progressed, I had occasion to notice instances of supernormal perception, and to test it I made use of the following expedient: Taking an old-fashioned copper cent, I carefully enveloped it in a piece of ordinary tissue paper. This was then covered by another and then another, until the coin had acquired six complete envelopes of the paper, and formed a little flat parcel, easily held in the palm of my hand.
Taking this with me, I visited my patient. She was lying upon a sofa, and as I entered the room I took a chair and sat leisurely down beside her, having the little package close in the palm of my right hand. I took her right hand in mine in such a manner that the little package was between our hands in close contact with her palm as well as my own. I remarked upon the weather and commenced the routine duty of feeling her pulse with my left hand. A minute or two was then passed in banter and conversation, designed to thoroughly engage her attention, when all at once she commenced to wipe her mouth with her handkerchief and to spit and sputter with her tongue and lips, as if to rid herself of some offensive taste or substance. She then looked up suspiciously at me and said:
“I wonder what you are doing with me now.”
Then suddenly pulling her hand away from mine she exclaimed:
“I know what it is; you have put a nasty piece of copper in my hand.”
Through all these coverings the coppery emanation from the coin had penetrated her system, reached her tongue, and was perceptible to her supernormal taste.