In fact, all the calligraphy pens in ancient China experienced a process of selecting materials. Early brushes were mainly hard hair, mostly rabbit hair, and the best was purple hair made of purple-black mountain rabbit hair. This kind of brush is quite hard, but it is not easy to handle. It wears away quickly when used, so it is quite expensive. However, because the output of wolf hair is greater than that of purple hair, and the price is not so high, wolf hair brush has gradually become a substitute for rabbit brush.
It is said that Wang Xizhi used a "parallel pen" when he wrote Preface to Lanting. If this pen is not a wolf's brush, it must be hard. Writing with this hard brush will show several characteristics: first, because of the limited water content of the brush, it can only be written on cooked rice paper or silk that does not absorb water. Second, because the pen itself cannot be made too big, the characters in early calligraphy works are generally small and medium-sized. Thirdly, because the bristle brush has the advantages of toughness and stiffness, it is excellent in showing the details of the stroke turning zone.
In contrast, the wool pen-that is, the pen made of goat hair-is actually quite late. Sheep hair is not as strong as wolf hair, belonging to soft hair, but because of its high output, it can also be made very big, so it is very suitable for writing big characters. People who have just started to practice calligraphy generally use sheep hair, which is very suitable for practicing regular script with large font and can be practiced with heavy brushwork. After learning to a certain stage, if you want to learn the calligraphy tradition of Jin and Tang dynasties that pays more attention to the details of strokes, you need to use Langhao more.
Summary: Wolf is better than Yang Haobi, so he should write and draw. It was originally made of wolf hair, and later it was changed into weasel hair, so today's wolf hair is not "wolf hair". What Lang Hao saw was recorded very late. The best brush was rabbit hair, followed by Lang Hao and wool.