Once upon a time, there was a Scottish school marm. She wrote a text about the laws of grammar and it became the standard text. However, in the same Dr Johnson made up/ choose his favorite spellings for words in his dictionary, many of the laws were pecadillos of the school marm - which is why splitting infinitives was considered incorrect for so long, and you couldn't (as I've just done) put an 'and' after a comma. Nowadays, many of these 'laws' are being disregarded since they do not simplify comprehension - which is, after all, the point of grammar.