Almost all object oriented languages have some syntax that distinghishes the reciever, to make it easier to understand the message passing expression. A common syntax is similar to accessing a data field, the reciever is listed, followed by a dot, followed by a message. However some language, such as Smalltalk, will use a different syntax. In any case, no matter what syntax is used, a message expression has three identifyable parts, the reciever, the selector, and the list of arguments. (The latter is optional in some languages, if there are no arguments).
The book describes the message passing syntax for several languages, we will not cover this here.