What are the Blackfoot shirts in the Pitt Rivers Museum made of?

Men on the northern Plains wore hide shirts for ordinary dress and protection from the weather and the brush, as well as for war and ceremonial purposes. Shirts were also worn on diplomatic occasions such as going to negotiate with other tribes or traders, and later for the negotiation of treaties with the US and British governments. Shirts and their decoration expressed the wearer's identity, and communicated something of his relationships with the natural and spiritual world. They might also communicate his spiritual and political power and significant events in the wearer's life. They were far more than just clothing.