Can not access related module's ID field.

[sudeepsnairontash]

I have a one-to-many relation between Contacts module and a custom module named 'Medical records'.
I have to create medical records using Sugarcrm gem and connect each medical records with corresponding Contact so that the list of medical records appear in the Medical records subpanel in Contacts module. But when I try to do this, I can not set the ID field of contact record through the relation field. There is a name field, but no ID field is there.
SugarCRM version:
Version 6.5.13 (Build 1041)
SugarCRM Ruby gem version: 0.9.18
Please help me.