With the arrival of advanced networks such as the Internet of Things (IoT), Internet of Nano Things (IoNT) and recently Internet of Bio-Nano Things, the necessity of perform accurate estimates as to the Bit Error Rate is manifested with a particular necessity in those networks where the signal pass through tissue. It is the case of the Biological Internet where absorption might large enough to increase the BER substantially. From the fact that this advanced Internet would require an unstoppable communication between sources and receptors, one might use the well-known Friis however in tissue this equation might be modified. In this paper we present the modified Friis equation that would be useful in that Biological Internet networks where the BER would turn to be low enough because the path loss.