Organization.

The assembly of members and honorary members convened at each session is the sovereign^[9]legislative body of the Institute.Executive power is vested in the Bureau of the Institute，an office composed of the president of the Institute，the three vice-presidents，the secretary-general，and the treasurer.

The president，usually chosen from among the members representing the country or institution which is to host the next session of the Institute，and the first vice-president are elected at the end of a given session and remain in office until the close of the following session.The second and third vice-presidents are elected at the opening of each session，remaining in office until the start of the next session.The secretary-general and the treasurer，elected to serve for three sessions，may succeed themselves.As the principal executive officer of the Institute，the secretary-general directs the daily operation of the Institute，assumes custody of its archives，and supervises publication of its Yearbook.His residence is the official seat of the Institute.3