The lingual sibilant ष् ṣ.
225. Since the lingual sibilant, in its usual and normal occurrences, is (182) the product of lingualization of s after certain alterant sounds, we might expect final radical ṣ, when (in rare cases) it comes to stand where a ṣ cannot maintain itself, to revert to its original, and be treated as a s would be treated under the same circumstances. That, however, is true only in a very few instances.
a. Namely, in the prefix dus (evidently identical with √duṣ); in sajū́s (adverbially used case-form from √juṣ); in (RV.) vivés and ávives, from √viṣ; in āíyes (RV.), from √īṣ; and in āçís, from çiṣ as secondary form of √çās. All these, except the first two, are more or less open to question.
226. In general, final lingual ष् ṣ, in internal combination, is treated in the same manner as palatal श् ç. Thus:
a. Before t and th it remains unchanged, and the latter are assimilated: e. g. dviṣṭas, dviṣṭhas, dvéṣṭum.
This is a common and perfectly natural combination.
b. Before dh, bh, and su, as also in external combination (145), it becomes a lingual mute; and dh is made lingual after it: e.g. piṇḍḍhi, viḍḍhi, viviḍḍhi, dviḍḍhvam, dviḍbhís, dviṭsú; bhinnaviṭka.
c. So also the dh of dhvam as ending of 2d pl. mid. becomes ḍh after final ṣ of a tense-stem, whether the ṣ be regarded as lost or as converted to ḍ before it (the manuscripts write simply ḍhv, not ḍḍhv; but this is ambiguous: see 232). Thus, after ṣ of s-aorist stems (881 a), astoḍhvam, avṛḍhvam, cyoḍhvam (the only quotable cases), from astoṣ + dhvam etc.; but arādhvam from arās + dhvam. Further, after the ṣ of iṣ-aorist stems (901 a), āindhiḍhvam, artiḍhvam, ajaniḍhvam, vepiḍhvam (the only quotable cases), from ajaniṣ + dhvam etc. Yet again, in the precative (924), as bhaviṣīḍhvam, if, as is probable (unfortunately, no example of this person is quotable from any part of the literature), the precative-sign s (ṣ) is to be regarded as present in the form. According, however, to the Hindu grammarians, the use of ḍh or of dh in the iṣ-aorist and precative depends on whether the i of iṣ or of iṣī is or is not “preceded by a semivowel or h” — which both in itself appears senseless and is opposed to the evidence of all the quotable forms. Moreover, the same authorities prescribe the change of dh to ḍh, under the same restriction as to circumstances, in the perf. mid. ending dhve also: in this case, too, without any conceivable reason; and no example of ḍhve in the 2d pl. perf. has been pointed out in the literature.
d. The conversion of ṣ to ṭ (or ḍ) as final and before bh and su is parallel with the like conversion of ç, and of j and h in the mṛj and
