The schematic below is of a CD4007 mos transistor chip. From the schematic it can be seen that on either side, pmos or nmos, the arrows indicating what type of mos transistor it is, are all connected to a single pin, pin 7 for the nmos side, and pin 14 on the pmos side. In this case, pin 7 is a source and pin 14 is a drain. Why is that? Does anything need to be connected to those pins to use the other transistor in the chip?