Step 1: Concept of admission of a partner.
When a new partner is admitted, the existing partnership agreement ends and a new agreement is created. However, the firm as a business entity continues to exist.
Step 2: Effect on the firm.
- The old partnership is dissolved legally, but not the firm itself.
- A new partnership is formed, including the new partner.
- This process is called "reconstitution of partnership."
Final Answer: \[ \boxed{\text{The old partnership is reconstituted.}} \]