10. The heart and arteries. 

 a. The Arteries. 

 Distend the oesophagus with a cylindrical piece of wood or a roll of paper, and 

 after carefully cleaning the aortic arches, study and make a diagram (4 

 nat. size) of the heart, truncus arteriosus, and the following arteries — 

 (a) The carotid arch, giving off 



(1) The lingual artery. 



(2) The carotid artery, which arises from the carotid gland, and 



divides into an external carotid branch and an internal carotid 



• branch — the latter entering the cranium supplies the brain. 



(6) The systemic arch (4th arch of fish, 2nd of tadpole) which bending 



round the oesophagus unites with its fellow of the opposite side to 



form the dorsal aorta. Each arch gives off the following branches 



before uniting — 



(1) The laryngeal artery. 



(2) The oesophageal arteries. 



(3) The occipito-vertebral artery. 



(4) The subclavian, for the shoulder and fore limb. 

 The dorsal aorta gives off — 



(1) The coeliaco-mesenteric which divides into (i) the coeliac for the 



stomach and liver, and (ii) the mesenteric for the intestines and 

 spleen. The coeliaco-mesenteric sometimes arises from the left 

 systemic arch. 



(2) The urino-genital arteries, for the kidneys, genital organs, and 



fatty bodies. 



(3) Lumbar branches for the body walls, and a small medium branch 



(hsemorrhoidal) for the large intestine. 



(4) The iliac arteries (the terminal bifurcation of the dorsal aorta) 



(which supply the bladder (hypogastric) and the anterior walls 

 of abdomen (epigastric) ; each then extends along the thigh as 

 a femoral artery, and each femoral divides into a tibial and 

 peroneal branch. 

 ((') The pulmo-cutaneous arch, dividing into 



(1) The pulmonary artery for the lung, and 



(2) The cutaneous which supplies the skin of the back and sends 



small branches to the side of the head. 



The thyroid gland is represented by small bright oval bodies in connection 

 with the lingual arteries, and between the systemic and pulmo-cutane- 

 ous arches, the thymus by two small round bodies, one behind each 

 suspensorium. The spleen lies near the large intestine, and the 

 adrenal glands are embedded in front of the kidneys. 



The mandibular branches of the 5th and 7th, and all the branches of the 

 9th and 10th cranial nerves, and of the 1st spinal nerve should now 

 be examined. For description see pages 26, 28, and 32. 



