When London's PA Consulting Group decided to apply its business system modeling software to the human body, the firm bit off more than it could chew. PA's Organ Systems Modelling subsidiary had begun work on software to build a model of the immune system over time before realizing the limitations imposed by a lack of expertise in biochemistry, said CEO Jeremy Asher. "Our understanding of physiology was simplistic," he said.

Meanwhile, Physiome Sciences Inc. had built a computer model of the human heart that predicts