Why did not transactions precede a length specification?

[MixMAx123]

Raw transactions in the blocks do not have any preceding lengths in the first bytes. Why?
How are the transactions within a block best parsed without the length specification within the transaction?

[achow101]

Transactions are self descriptive in length. Any field that is variable length contains its length, All other fields are fixed length and a parser knows this. So transactions don't need length prefixes because a parse will know when a transaction ends, and the next bytes are the beginning of the next transaction.

[MixMAx123]

Ok, I could have come up with that myself.
Many thanks