Assertion: porcupine's spike | /r/MadeOf | the protein keratin
Facets:
Source sentences:
text: The spikes of the hedgehog are hollow hairs that are made from the protein keratin (the same stuff that human hair and fingernails are made from), and unlike the spikes of the porcupine, the spikes of the hedgehog cannot be removed easily.
text: The spikes of the hedgehog are hollow hairs that are made from the protein keratin (the same stuff that human hair and fingernails are made from), and unlike the spikes of the porcupine, the spikes of the hedgehog cannot be removed easily.