Additionally, pulse diagnosis is an integrative part of traditional Chinese medicine. With spectral analysis of the pulse waves, researchers started to observe the pulse wave harmonics. An in vivo study of rats revealed that ligating one or both of the renal arteries significantly reduced the second harmonic component of the pressure pulse at the caudate artery. Ligating the artery toward the spleen prominently reduced the third harmonics component of the pulse. Analysis of the harmonics in the spectrum of the arterial pressure wave revealed that individual organs might have their own natural frequencies. These observations suggested that individual vascular beds exert independent, frequency-specific, effects on the peripheral pressure wave.