Chords are usually used in the separated form on the bass, in correspondence with a style of performed music. As a bass isn't a one-voice instrument, it is quite possible (during a solo or if an arrangement requires it) to use triads and seventh chords, performing all sounds simultaneously, similar to guitarists. The reason for a rare usage of chords in the harmonic way on the bass is the thickness of strings. The thicker the string is, the easier it is to elicit flageolets, and flageolets are actually overtones. In other words, the thicker the string is, the louder are overtones, hidden behind the main tone. When we perform four sounds simultaneously on a bass, all these notes with their overtones blend with each other and so fully overlap the frequency range, that there is nothing for it but to shout such an accompaniment down. So, to improve this situation, arranged chords are used. The main point of this chord arrangement is that besides doubling notes and octave repetitions, you can also miss degrees, which don't affect the harmonic function of a chord; those are the I (first) and the V (fifth) degrees. As a result we get stated below shapes of arranged chords.