You said in your original post "but instead transmitted the data through the usb cable to my mac."
Does that mean you have the arduino plugged in through its usb connection.
If so then this is the first problem. The usb connection on the arduino will not be considered a midi device by the computer as its usb declaration is that it is a serial port . This means the signals you are sending don't go into the midi processing part of the computer, so will not show up as midi even if the signals are correct midi info.
To get them into the midi system the easiest way is to take the serial signal from pin 1 of the arduino board and connect this to a commercial midi to usb convertor
More detail here
http://itp.nyu.edu/physcomp/Labs/MIDIOutput
HTH
Nick