Why doesn't the content show up

Following this tutorial on uploading a file:
http://www.dizzy.co.uk/ruby_on_rails/contents/store-file-uploads-in-database#rendering_an_image_stored_in_the_database

I reached: "3. Rendering an image stored in the database".

But, before commencing with that, I tried to create a new entry, and NO
fields show any data except for the description for example where I
entered its data in the form. Why is that?

Thanks.