Now, this purple section is the basement membrane that is shown in this diagram. It's this purple outline that goes all the way around our Bowman's capsule. So this purple layer is the basement membrane. It consists of a network of proteins, and it contains a negative overall charge. And what that basically means is negatively charged particles such as chloride ions will find it very difficult to actually pass across the basement membrane because of that propulsion between the negative charge of the chloride ion and the negative charge of the basement membrane. So we see that positively charged particles will be attracted across, but negatively charged particles will tend to stay within the blood vessels of Araglomerilus.