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The making of the virtual heart 133

The Physiome Project will build on linking descriptions of biological
function and structure. On a macroscopic level, this will benefit from
another on-going large-scale research effort – the Visible Human Project.
This is an expansion of the 1986 long-range plan of the US National Library
for Medicine to create anatomically detailed, three-dimensional represen-
tations of the human anatomy. The project is based on collecting trans-
verse computer tomography, magnetic resonance, and cryosection images
at 0.5–1mm intervals. This spatial resolution is sufficient to develop initial
models of biological function, in particular where these are related to
macro-mechanics or passive electrical properties. A finer resolution will,
however, be required in the context of anatomico-functional modelling at
tissue level and, almost certainly, when addressing inter-cellular or sub-
cellular events.

8.3.2 The route
So much about the vision – what about the route? The Physiome Project
will – like the Genome and Visible Human projects – crucially depend on
the ability to develop the necessary tools for its own successful implemen-
tation. Apart from obtaining useful data and building representative data-
bases, this primarily includes the capacity to devise appropriate algorithms
to model physiological function.
But – why model?
The concise Oxford dictionary of current English defines a model as ‘a
simplified . . . description of a system etc., to assist calculations and pre-
dictions’. One can apply this definition in its wider sense to any intellec-
tual activity (or its product) that tries to make out the components of a
system and to predict the outcome of their interaction. Thus, to think is
to model (beware, though, that the reverse is not necessarily true).
To implement the Physiome Project, a lot of ‘good science’ (Wolpert)
and ‘thinking’ (Dover) will be required. The tools that will ultimately
define the success of the project are analytical models of biological pro-
cesses that have predictive power – virtual cells, tissues, organs and
systems.
This will extend, and partially replace, the traditional approach to bio-
medical research that is based on studying living cells or tissues in vitro,
or on obtaining data from human volunteers in vivo, by introducing ‘in
silico’ experiments (a term, derived from the currently prevailing silicon-
based computer chips).