The mouth is here described as the chief or the most important gate. The mouth is a very important entrance because one has two functions to conduct with the mouth. One function is eating, and the other is speaking. Our eating is done with the friend Rasajna, the tongue, which can taste so many different types of foods. The tongue is also used for speaking, and it can speak of either material sense enjoyment or Vedic knowledge. Of course, here material sense enjoyment is stressed. Therefore the word rasajna is used.