Procter & Gamble Co. plans to invest $325 million in cash and provide marketing in a joint venture it will form with Inverness Medical Innovations Inc. Under terms of the agreement, each company will own 50% of the venture for medical tests outside of the fields of cardiology and diabetes. P&G will sell and distribute medical-diagnostic devices developed by Waltham, MA-based Inverness, which makes home pregnancy and fertility tests, under the joint venture, which each company will equ...