82 
ZOOLOGY, 
for the ingress of the venous blood. The colorless blood 
is pumped by the heart backwards and forwards through 
three anterior arteries, one median and two lateral, the 
median artery passing towards the head over the large 
stomach, and the two lateral, or hepatic arteries, passing 
to the liver and stomach. From the posterior angle of the 
heart arise two arteries; the upper, a large median artery 
(the superior abdominal), passes along the back to the erd 
of the abdomen, sending off at intervals pairs of smull 
arteries to the large masses of muscles filling the abdomi- 
nal cavity; the lower is the second or sternal artery, which 
connects with one extending along the floor of the body 
near the thoracic ganglia of the nervous cord. There are 
no veins such as are present in the Vertebrates, but a series 
of venous channels or smuses, through which the blood re- 
turns to the heart. There is, however, a large vein in the 
middle of the ventral side of the body. 
The blood is driven by the heart through the arteries, and 
Fig. 97. — C, first maxillipede of lobster. 
a large part of it, forced into the capillaries, is collected by 
the ventral venous sinus, and thence passing through the 
gills (Fig. 97, gill^ where it is oxygenated, returning to 
the heart. 
The gills are appendages of the three pairs of maxilli- 
pedes and the five pairs of feet, and are contained in a 
chamber formed by the carapace; the sea- water passing into 
the cavity between the body and the free edge of the carsir 
