= Solution
\b[The <liver> has a substantial normal range of size, determined by age, body dimensions, nutritional state and its variable contents; there is no universal absolute minimum and maximum valid for every healthy person.] One must also distinguish true organ volume from the position of its lower border, which moves with the <respiratory diaphragm> during <breathing>.
An ordinary adult <liver> is on the order of 1.5 kg and roughly a few percent of <body mass>, but neither figure is a diagnostic boundary. As an explicitly modern example, an autopsy study of adult men reported a mean hepatic mass of 1561 g and observed values from 838 to 2584 g in its selected population. Those are sample observations, not a declaration that every <liver> inside those limits is healthy or that every one outside is diseased. A newer large-sample study similarly found an association of liver mass with <body mass>; much of an apparent sex difference disappears when body size is taken into account.<Normal organ weights in men: part II—the brain, lungs, liver, spleen, and kidneys>[Abstract and reported organ-mass data; selected male autopsy population, 2012]{ref}<Updating Normal Organ Weights Using a Large Current Sample Database>[Results and Conclusions: liver mass, body size and sex after adjustment]{ref}
Age changes the proportion as well as the absolute size. The fetal and infant <liver> is relatively large; the adult organ is smaller in proportion to the whole body. Its fetal role in <haematopoiesis> and subsequent changes of growth and function make an adult mass standard inappropriate for an infant. Constitutional body size and normal anatomical shape also vary: a long lower projection is not necessarily the same thing as an enlarged total organ.
Reversible differences within one person arise because the <liver> is a store and a vascular organ:
* <Glycogen> is accumulated after suitable feeding and mobilized during fasting and exercise. Its storage is associated with <water>, so changing <glycogen> stores changes more than the dry mass of the stored <glucose> units.
* Hepatic <lipids> and their turnover also contribute to variation. This does not make substantial <hepatic steatosis> a normal consequence of every meal or justify treating pathological fatty enlargement as physiological.
* The amount of <blood> contained in the <hepatic sinusoids> and larger vessels can change with circulation and posture. Physiological vascular filling must be distinguished from persistent congestion caused by <heart failure>.
* Hydration and longer-term nutritional state influence the organ and its stores. Severe wasting or a persistent progressive enlargement requires a different explanation from a reversible difference between standardized fed and fasted observations.
A meal therefore changes hepatic activity and <splanchnic blood flow> without requiring a large immediate increase in total liver volume. In a modern paired study of 20 healthy volunteers, <single-photon emission computed tomography> before and after a standardized meal showed a nonsignificant 1.5% decrease in estimated liver volume. The authors judged the change to be within methodological error. This is a useful check against assuming that greater digestive activity proves gross swelling.<Effect of food intake on liver and spleen volume: assessment with single photon emission computed tomography>[Abstract: standardized meal, paired measurements and liver-volume result, 1997]{ref}
The experimental approach is to compare like with like: specify age and <body mass>, use a fixed interval after food, standardize hydration, posture and respiratory phase, and distinguish a volume measurement from a palpable edge or a single linear dimension. <Magnetic resonance imaging> can measure volume while <magnetic resonance spectroscopy> measures <glycogen> or <lipid> signals; the two observations answer different questions. The size of an excised organ additionally depends on how much <blood> remains in it. The physiological point appropriate to the 1866 question is reversible variation with growth, alimentation and vascular filling. Modern imaging results refine that point; they are not numerical standards that the historical exam could have expected.
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