DISEASES OF THE HEART IN DOMESTIC ANIMALS. 
161 
vital and nutritious material with the blood to the whole organ¬ 
ism, on the other hand to oxydize the previously carbonized blood 
of the organism through the lungs. The procedure of this pro¬ 
cess, which is mechanically very complicated, occurs in the fol¬ 
lowing manner: 
The action of the heart is explained by two movements, which 
follow upon one another in regular rhythm. These rhythms, by 
the active drawing together of the muscular walls, cause contrac¬ 
tion of the heart’s cavities—systole; and the passive b.y the relax- 
tion of the muscle of the heart cause expansion of the cavities— 
diastole. But systole and diastole cannot occur simultaneously in 
all four cavities of the heart, as the muscles of the ventricles and 
auricles do not stand in immediate connection, but are separated 
by the auriculo-ventricular valves. The systole begins at the 
same time and with the same energy in the two auricles, in order 
to end simultaneously; it begins at the orifice of the veins and 
continues forward to the auriculo-ventricular opening; at the 
same time the ventricle is in a diastole condition. The impulsive 
force of the auricle is not very great, nor does it require much 
force; the blood conveyed through the veins, which the impulsive 
force pumps into the cavities, could reach its destiny without 
special pressure. Immediately after the systole of the auricle, 
the systole of the ventricle commences simultaneously and with 
energy in all parts of the walls of the ventricle. The contrac¬ 
tion (systole) of the ventricle lasts somewhat longer than that of 
the auricles and collapses with its diastole. The diastole of the 
ventricle follows quickly upon its systole before the systole of the 
auricle commences; or during a very short time the four cavities 
of the heart are in a state of relaxation as if for recovery. There¬ 
upon a contraction of the auricles takes place, and the rhythm of 
the heart’s movements takes its progressive course.* 
Accordingly there are three tempii of the rhythmical action of 
the heart to be distinguished. They follow one another in rapid 
succession: 1—Tempo; systole of the auricle, disatole of the 
ventricle. 2—Tempo; disatole of the auricle, systole of ventri- 
* Cf. Muller, Function des Herzeus. 
