If {TAIL ~ the message} is understood by {HEAD ~ the referenced object}, then the method is executed in accordance with the message sent, and operation is completed as to the particular message 
If { TAIL ~ the message } is understood by { HEAD ~ the referenced object } , then the method is executed in accordance with the message sent , and operation is completed as to the particular message
OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH