On food and cooking the science and lore of the kitchen ( PDFDrive ) 238

partoftheanimal,andorganmeats,such
innardsastheliver,kidneys,intestine,andso
on.
TheEssenceoftheAnimal:MobilityfromMuscle

Whatisitthatmakesacreatureananimal?
ThewordcomesfromanIndo-Europeanroot
meaning“tobreathe,”tomoveairinandout
ofthebody.Thedefinitivecharacteristicof
animalsisthepowertomovethebodyand
nearbypartsoftheworld.Mostofourmeats
aremuscles,thepropulsivemachinerythat
movesananimalacrossameadow,orthrough
theskyorsea.
Thejobofanymuscleistoshortenitself,
orcontract,whenitreceivestheappropriate
signalfromthenervoussystem.Amuscleis
madeupoflong,thincells,themusclefibers,
eachofwhichisfilledwithtwokindsof
specialized,contractileproteinfilaments
intertwinedwitheachother.Thispackingof


proteinfilamentsiswhatmakesmeatsucha
richnutritionalsourceofprotein.An
electricalimpulsefromthenerveassociated
withthemusclecausestheproteinfilaments
toslidepasteachother,andthenlocktogether
bymeansofcross-bridging,orformingbonds
witheachother.Thechangeinrelative
positionofthefilamentsshortensthemuscle

cellasawhole,andthecrossbridgesmaintain
thecontractionbyholdingthefilamentsin
place.
Portable Energy: Fat Like any machine, the
muscle protein machine requires energy to
run.Almost as important to animals as their
propulsive machinery is an energy supply
compact enough that it doesn’t weigh them
downandimpedetheirmovement.Itturnsout
that fat packs twice as many calories into a
givenweightascarbohydratesdo.Thisiswhy
mobile animals store up energy almost
exclusively in fat, and unlike stationary