Date of Submission


Date of Award


Institute Name (Publisher)

Indian Statistical Institute

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Subject Name



Research and Training School (RTS)


Rao, C. Radhakrishna (RTS-Kolkata; ISI)

Abstract (Summary of the Work)

Tongue pigmentation in man:The 'partioular' type of dark apots and patohes on the surface of the tongue, as investigated in the prosent thesis, wae first not ioed in human populations by Davis [5], who called it 'tongue piementation'. It is to be emphasized that not all colour piements come under this 'particular' type. There are some pathological conditione giving rise to transient discolouration of the tongue. This aspeot will be disouesed a little later. Such tongue pigmentation does not seem to have been reported for any population, human or otherwise.Tongue pigmentation be usually found on the upper surface or borders (rim) of the tongue. In most of the cases, the spots were observed on the upper surface including the tip of the tongue, and the patohes on the borders, right and left. It may be recorded here that out of all the tongue pigmented peophe seen so far, nearly 80% ahowed only spots, 15% ahowed only patchas and the rest showed both spote and patches. Very fex individuale had thie pigmentation on the interior eurfade and/nr the borders of the tongae. Thus, one may have either exclusively spots or patohes, otherwise both. The trait exhibits variation in the number as well as the distribution of the spots and patohes, and also in the size and shape of the latter. Thero may be one epot to many spots, isolated or clustered, and patohes from the size of about 2 8q. mm. to as large a size as covering nearly half of the tongue surface. Out of several thousand examined ao far only one was obeerved showing just one spot covering an area of nearly 0.5 sq. mm. on the deep interior surface.Some obeervations indicate that the trait ie not subject to any changes over time. For example, I bécame aware of a pateh of about 1 sq. om. on my tongue in 1964, but there has not been any change of any sort till now, either in respeot of its size or intensi ty of the oolour of this pigmentation. Also, at the time of the tongue examination, most of the literate and pigmented subjenta were asked as to whether they remembor to have had it since birth. In aome case s, their parents were interrogated about it. Though in most of the cases the reply was "I am not sure", quite a few of them oonfirmed to have it unchanged ever since they firet noticed it on their tongues. This provides an encouraging evidence in favour of the above contention.Method of examination:The subject was asked to wide open the mouth, extending the tongue outward frontally as far as possible. Most of the tongues were examined in the diffused day-light, though a few had to be examined under torchlight. Generally, the South Indian women were rather shy to show their tongues especially in the presence of othera. But most of them could be persuaded to show the tongue, though examination had to be done under torchlight inside their houses.


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Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


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