In　recent　years,　the　increasing　number　of　wearable　devices　on　human　has　been　witnessed　as　a　trend.　These　devices　can　serve　for　many　purposes:　personal　entertainment,　communication,　emergency　mission,　health　care　supervision,　delivery,　etc.　Sharing　information　among　the　devices　scattered　across　the　human　body　requires　a　body　area　network　(BAN)　and　body　sensor　network　(BSN).　However,　implementation　of　the　BAN/BSN　with　the　conventional　wireless　technologies　cannot　give　optimal　result.　It　is　mainly　because　the　high　requirements　of　light　weight,　miniature,　energy　efficiency,　security,　and　less　electromagnetic　interference　greatly　limit　the　resources　available　for　the　communication　modules.　The　newly　developed　intra-body　communication　(IBC)　can　alleviate　most　of　the　mentioned　problems.　This　technique,　which　employs　the　human　body　as　a　communication　channel,　could　be　an　innovative　networking　method　for　sensors　and　devices　on　the　human　body.　In　order　to　encourage　the　research　and　development　of　the　IBC,　the　authors　are　favorable　to　lay　a　better　and　more　formal　theoretical　foundation　on　IBC.　They　propose　a　multilayer　mathematical　model　using　volume　conductor　theory　for　galvanic　coupling　IBC　on　a　human　limb　with　consideration　on　the　inhomogeneous　properties　of　human　tissue.　By　introducing　and　checking　with　quasi-static　approximation　criteria,　Maxwell＇s　equations　are　decoupled　and　capacitance　effect　is　included　to　the　governing　equation　for　further　improvement.　Finally,　the　accuracy　and　potential　of　the　model　are　examined　from　both　in　vitro　and　in　vivo　experimental　results.