NERVOUS SYSTEM OF VERTEBRATES. 371 
called the lacteal system or absorbents, which take up a part 
of the chyle from the digestive organs and convey it to the 
blood-vessels, r 
There is a true heart, with one, generally two, auricles, and 
one or two ventricles with thick, muscular walls, and besides 
arteries and veins, a capillary system, 7. e., minute vessels 
connecting the ends of the smaller arteries with the smaller 
veins. There are no genuine capillaries in the lower animals 
exactly comparable with those of the Vertebrates. 
The blood is red in all the Vertebrates except the lancelet, 
and contains two sorts of corpuscles, the white corpuscles 
like the blood-corpuscles of invertebrates, and red corpuscles 
not found in invertebrates, and which are said by some 
authors to be derived from the white corpuscles, 
While fishes and larval Amphibians breathe by gills, all land 
and amphibious Vertebrates breathe the air directly by means 
of cellular sacs called lungs, and connected by a trachea with 
the pharynx, the trachea being situated beneath the cesopha- 
gus, and the opening from the mouth into the pharynx lead- 
ing into the trachea being placed below the throat or passage 
to the esophagus. The air filling the cells or cavities of the 
lungs passes by osmose through the walls of the cells into the 
blood sent by the heart through the pulmonary artery, and 
after being oxygenated, the blood returns by the pulmonary 
vein to the heart. On the other hand, carbonic acid passes 
from the blood out of the lungs through the trachea. 
The nervous system of Vertebrates consists of a brain and 
spinal cord. The brain consists of four pairs of lobes, i. ¢., 
the olfactory lobes, cerebral hemispheres, the optic thalami 
(Thalamencephalon) and pinealgland,*and the optic lobes; and 
two single divisions : the cerebellum and the beginning of the 
spinal cord, called the medulla oblongata. The olfactory lobes 
are the most anterior, and send off the nerves of smell to the 
nose. The cerebral hemispheres in the fishes and amphibians 
are little larger than the adjoining lobes, but in the reptiles 
become larger, until in the mammals, and ‘especially in the 
apes and man, they fill the greater part of the brain-box and 
overlap the cerebellum ; the latter, in the mammals, also 
exceeding all the other lohee 3 in size, excepting the cerebrum. 
* This proves to be the rudiment of the median eye. 
