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But the movements of the abdomen that accompany the systole 
of the heart, are more complicated. 
1. A group of hairs on the central part of the back ‘do not 
change place parallelly as would be the case, if they simply took 
part in the general rotation of the abdomen; they make a rhythmical 
oscillating movement, which can only be the result of a special 
deformation of the field,’ on which they have been infixed. This 
deformation consists in a rhythmical descent of the part we had in 
view, corresponding with the descent of the entire abdomen. It is 
caused by a tension in the ligaments epicardiques (especially 3 to 9) 
which accompanies the systole of the most active part of the heart. 
2. The region of the median dorsal line, lving quite frontal, just 
over the peduncle, is pushed forward about +4, millimeter in a 
frontal direction at the beginning of every pulsation (when the 
abdomen descends): at the beginning of the general contraction of 
the heart-tube the motion of the blood causes there a tumefaction 
of the vessel of short duration. 
3. The exterior wall of the lungs shows likewise very slight 
oscillations and descends to the interior at every systole : a phenomenon 
indicating a decrease of the pressure of the blood under this region. 
This leads us to the study of the influence of the systoles of the 
heart on the contents of the lungs. I have been able to make a 
special study of this subject with another species of spider possessing 
transparent teguments, allowing us distinctly to observe some move- 
ments of the interior organs. 
With Pholeus phalangioides one observes similar movements and 
variations of the shape of the abdomen as with pera, but these 
are still more complicated, because the teguments are more flexible, 
and correspond more to the local variations of the interior pressure ; 
yet I shall for the present moment not describe them more accurately. 
A direct observation convinces us that the contraction of the heart 
eauses a diminution of the pressure of the blood in the pericardial 
‘avity and in the pulmonary vein: the laps of the “liver” surrounding 
these blood-cavities are seen to move inwardly at every systole, 
and the more violently as the examined point lies nearer to the 
most active part of the heart. 
The same phenomenon shows likewise a similar diminution of 
the pressure in the large blood-lacune in which the heart lies; conse- 
quently there exists a suction of the blood from the peripulmonary 
lacuna to the pulmonary vein, and likewise, which is of importance 
for the respiration, from the lacunes of the lamellas of the lung: a 
sufficient illumination allows us even to see, that, when a systole 
