This article focuses on the function of the convict prison

infirmary and views it as a site of arbitration, resistance and ‘contested

power’. In accordance with the rules and regulations periods of

incarceration in convict prisons began and ended with an obligatory

medical examination. While the primary function of the initial test

was to measure the convict body in order ascertain physical ability

to conduct hard labour it also provided a thorough bio-metrical

description for future identification purposes. The final examination

was not as comprehensively undertaken but also concerned itself with

anthropometrical observations. It would be reasonable to assume that the

balance of power was weighted in the authority’s favour but this research

has found evidence to the contrary. For instance, that there was a fair

degree of physiological knowledge within the convict population and

that some convicts used the infirmary for dietary gains and reprieve from

hard labour. Using body mass index (BMI) as an instrument to measure

physical wellbeing this article views the doctor–convict interface as

a crucial component of the penal experience. It analyses 251 convict

medical records to show that the balance of diet and work led to what

might be considered a counterintuitive outcome – a preponderance of

weight gain, particularly for males in Irish prisons.