Before: attachments not in body of letter. Now: attachments in body of letter - not wanted so. How do I fix?

A few days ago when I used Thunderbird in sending e-mail messages as I would place an attachment it would just stay as an attachment and there was not change to what I had entered in the body of the message. Now when I make an attachment to an e-mail message, the attachment holds with the message, but also becomes part of the body of the message. i.e. form or picture now showing in full in body of e-mail message. I want to know how to change Thunderbird back so the attachments just stay attachments only. Thanks.