  Continuous multi-channel monitoring of biopotential signals is vital in
understanding the body as a whole, facilitating accurate models and predictions
in neural research. The current state of the art in wireless technologies for
untethered biopotential recordings rely on radiative electromagnetic (EM)
fields. In such transmissions, only a small fraction of this energy is received
since the EM fields are widely radiated resulting in lossy inefficient systems.
Using the body as a communication medium (similar to a 'wire') allows for the
containment of the energy within the body, yielding order(s) of magnitude lower
loss than radiative EM communication. In this work, we introduce Animal Body
Communication (ABC), which utilizes the concept of using the body as a medium
into the domain of chronic animal biopotential recording. This work, for the
first time, develops the theory and models for animal body communication
circuitry and channel loss. Using this theoretical model, a sub-inch$^3$,
custom-designed sensor node is built using off the shelf components which is
capable of sensing and transmitting biopotential signals, through the body of
the rat at significantly lower powers compared to traditional wireless
transmissions. In-vivo experimental analysis proves that ABC successfully
transmits acquired electrocardiogram (EKG) signals through the body with
correlation accuracy >99% when compared to traditional wireless communication
modalities, with a 50x reduction in power consumption.
