If several properties belonging to several persons are mortgaged to secure a debt due to taking of a loan, the law says that each property should contribute towards the debt in proportion to its value. This is called the doctrine of contribution.
This doctrine is contained in Section 82 of the law of Transfer of Property. This law refers to the scheme of rateable distribution.
If some persons takes a loan from one person by mortgaging their separate properties which may be of different values and the mortgagee/creditor realises the loan amount from only one of the properties, the owner of such property can compel the other property owner to contribute in proportion to its value for the amount realised by the mortgagee.
For example if the property X belongs to A and the property Y belongs to B, and A and B jointly executes a mortgage of both the properties for securing a loan taken from C. Later C realised the debt from property X alone. In this case B must contribute rateably in proportion to the value of his property Y. Here A can claim contribution from B.