GO GENERAL BIOLOGY 



ophthalmic artery to the eye. There is a little swelling known as the 

 carotid gland at the point where the common carotid branches. 



II. The pulmo-cutaneous ( ) artery forms the 

 pulmonary artery, passing to the lungs, and the cutaneous artery. The 

 cutaneous in turn gives off the auricularis ( ) dis- 

 tributed to the lower body and neighboring parts, the dorsalis which 

 supplies the skin of the back, and the lateralis which supplies the skin on 

 the sides. Most of these branches also carry blood to the various respi- 

 ratory organs, lungs, skin, and mouth. 



III. The systemic arches pass outward, around the digestive canal, 

 and then unite to form the dorsal aorta. Each systemic arch gives off 

 an occipito-vertebral artery which divides ; one branch, the occipital, 

 ( ) supplying the jaws and nose; the other, again 

 dividing forms the vertebral, supplying the spinal cord and muscles of 

 the body wall, and the subclavian which is distributed to the shoulder, 

 body-wall and arm. The dorsal aorta gives off the coeliaco-mesenteric 

 artery. This divides, forming the coeliac which supplies the stomach, 

 pancreas, and liver, and the anterior mesenteric, which is distributed un- 

 der the intestine, the spleen, and the cloaca. Back of the origin of the 

 coeliaco-mesenteric, the dorsal aorta gives off four to six urinogenital 

 arteries which supply the kidneys, reproductive organs, and fat bodies. 

 A small posterior mesenteric artery arises near the posterior end of the 

 dorsal aorta passing into the rectum. In the female this artery also sup- 

 plies the uterus. The dorsal finally divides into two common iliac 

 ( ) arteries which are distributed into the ventral 

 body-wall, the rectum, bladder, the anterior part of the thigh (here called 

 femoral artery), and other parts of the hind limbs (sciatic artery). 



All the arteries finally break up into a vast number of microscopic 

 thin-walled vessels called capillaries (Lat. capillus=hair) by which 

 every part of the body is reached. 



THE VEINS 



The veins (Fig. 14) return the blood to the heart by draining all 

 parts through venous capillaries ; the veins reversing the arterial system 

 by constantly becoming larger and larger. It will be, noted here that the 

 blood vessels thus form a closed system and the blood that leaves the 

 heart returns without leaving the vessels. "The blood from the lungs is 

 collected in the pulmonary veins and poured into the left auricle. The 

 rest of the venous blood is carried to the sinus venosus by three large 

 trunks, the two anterior venae cavae ( ) and the 



posterior vena cava. The anterior venae cavae receive blood from the 

 external jugulars ( ) which collect blood from the 



tongue, thyroid, and neighboring parts, the innominates which collect 

 blood from the head by means of the internal jugulars and from the 

 shoulder by means of the subscapulars, and the subclavians which col- 



