60 General Biology 



I. The common carotid ( ) divides into the 

 lingual or external carotid, supplying the tongue and neighboring parts, 

 and the internal carotid which gives off the palatine ( ) 

 artery to the roof of the mouth, the cerebral carotid to the brain and the 

 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 respira- 

 tory 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, 

 ( ) supplies the jaws and nose; the other again 

 divides to form the vertebral which supplies 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 

 under 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 

 supplies 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 run in the opposite direction 

 of the arteries and constantly become larger and larger. It will be noted 

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

 the heart returns to the heart without leaving the vessels. The blood 

 from the lungs is collected by the pulmonary veins and poured into the 

 left auricle while the rest of the venous blood is carried to the sinus 

 venosus by three large trunks. There are two anterior venae cavae 

 ( ) and one posterior vena cava. The anterior venae 



cavae receive blood from the external jugulars ( ) 



which collect the blood from the tongue, thyroid, and neighboring parts, 



