Current Conveyor CCII internal circuital realization
Kinka-Byo, remember the classical opamp with feedback. 


The transistors M1, M2, M5 and M6 form a high-gain amplifier (output node: between M5 and M6) - and the connection between the output node and the input X provides 100% negative feedback (the input X acts as an inverting input). Hence, as for the classical opamp the input voltage at Y (non-inverting) is amplified with "1" (unity gain amplifier) and the output voltage is also identical to the voltage at X. 
According to system theory (and for current feedback), the input resistance at the feedback node is lowered by a factor which is identical to the loop gain. For a high loop gain, the input resistance (at X) is considerably lowered.   
The combination M7/M8 is identical to M5/M6 and both combinations receive the same input at the base nodes. Therefore, when there is a current through the input X we have the same current through a load that is connected to the high-resistive output Z.