ṣ is substituted for the s of sthala after vi , ku , śami and pari,
Thus विष्ठलम्, कुष्ठलम्, शमिष्ठलम् and परिष्टलम् ॥ The word वि, कु and परि are compounded under 2.2.18; the word शमी forms a genitive by 6.3.63. In the aphorism the word शमि is shown with a short इ, indicating thereby that when the इ is not shortened, the cerebral change does not take place; as शमीस्थलम्,