In fact, the four tones appeared and were discovered with the translation of Buddhist scriptures. Four tones means that Chinese characters have four pronunciations: even tone, rising tone, falling tone and entering tone. Modern Chinese has no entering tone. In fact, from the Yuan Dynasty, Rusheng gradually disappeared in spoken language. That's understandable. Because Yuan people, as the northern regime, were mostly vague and unable to make a sound. Rusheng words are particularly short to read, which is simply a high requirement for northerners.
So gradually evolved into today's China people, only Yin Ping, Yang Ping, Shang Sheng, Desheng. In other words, the ancient Rusheng characters have been decomposed into other rhymes.
Eight diseases refer to eight prosodic problems that should be avoided in poetry creation. They are:
Flat head, upper tail, bee waist, crane knee, big rhyme, small rhyme, side buckle, positive buckle.
Attachment: Shen Yue and others began to study the theory of temperament and sick criminals in poetry as early as the Southern Dynasties. "The Biography of Southern History and Lu Biao" says: "This is an article, Chen. I, nirvana in fire Wang Rong, push each other. Zhou Qingshan of Runan interprets phonology, and all his works are palace merchants, divided into four tones. With this rhyme, there are flat head, upper tail, bee waist and crane knee. In the five characters, the phonology is different, and within two sentences, the horn number is different, which cannot be increased or decreased. The world is called the eternal body. "