592 THE VASCULAR SYSTEMS 



deserves, owing to the fear which surgeons have entertained of secondary hemorrhage, on account 

 of the number of branches given off from the vessel. This fear, however, has been shown by 

 Mr. Cripps not to be well founded. 1 Ligation is often very useful as a means of preventing 

 excessive hemorrhage in operations about the face, jaws, and mouth. It is sometimes employed 

 with the hope of lessening the growth of tumors by cutting off the blood supply, but ligation is 

 useless for this purpose. Ligation of one external carotid artery arrests the circulation for only 

 a brief period, and within a very few days the circulation is practically freely reestablished. 

 This result is seen to be inevitable when we recall the numerous branches of the external carotid, . 

 their free anastomoses, and the fact that a very great number of extremely minute vessels in 

 the middle line join the external carotid system of one side to that of the other side. Robert 

 H. M. Dawbarn points out that ligation of both external carotids produces only temporary 

 anemia, for "inside of a week or ten days thereafter the pulse can again be felt in the temporals 

 and facials upon both sides." 2 Dawbarn points out that even after excision of the external 

 carotids, with separate ligation of each of the eight branches, blood can still reach the nose, 

 tongue, etc., from outside systems by twenty-nine distinct routes. Whereas ligation of even both 

 carotids will not prevent the growth of a malignant tumor, excision of each external carotid, 

 with separate control of its eight branches, will sometimes prove of great value in retarding the 

 progress of a growth. It "starves" the growth and may cause it to shrink (Dawbarn's oper- 

 ation). To tie the external carotid near its origin, below the point where it is crossed by the 

 Digastric, an incision about three inches in length should be made along the margin of the Sterno- 

 mastoid, from the angle of the mandible to the upper border of the thyroid cartilage. The ligature 

 should be applied between the lingual and superior thyroid branches. To tie the vessel above 

 the Digastric, between it and the parotid gland, an incision should be made, from the lobe of the 

 ear to the greater cornu of the hyoid bone, dividing successively the skin, Platysma, and fascia. 

 By drawing the Sternomastoid outward, the posterior belly of the Digastric and Stylohyoid 

 muscles downward, and separating them from the parotid gland, the vessel will be exposed, 

 and a ligature may be applied to it. The circulation is at once reestablished by the free com- 

 munication between most of the large branches of the artery (facial, lingual, superior thyroid, 

 occipital) and the corresponding arteries of the opposite side and by the anastomosis of its 

 branches with those of the internal carotid, and of the occipital with the branches of the sub- 

 clavian, etc. 



Branches. The external carotid artery gives off eight branches, which, for 

 convenience of description, may be divided into four sets. (See Fig. 439, Plan of 

 the Branches.) 



Anterior. Posterior. Ascending. Terminal. 



Superior Thyroid. Occipital. Ascending Phar- Superficial Temporal. 



Lingual. Posterior Auric- yngeal. Internal Maxillary. 



Facial. ular. 



The student is here reminded that many variations are met with in the number, 

 origin, and course of these branches in different subjects; but the above arrange- 

 ment is that which is found in the great majority of cases. 



1. The superior thyroid artery (a. thyroidea superior} (Figs. 438 and 439) 

 arises from the external carotid artery, just below the greater cornu of the hyoid 

 bone, and terminates in the thyroid gland. 



Relations. From its origin under the anterior border of the Sternomastoid it runs upward 

 and forward for a short distance in the superior carotid triangle, where it is covered by the 

 integument, fascia, and Platysma; it then arches downward and forward beneath the Omo- 

 hyoid, Sternohyoid, and Sternothyroid muscles. To the inner side are the Inferior constrictor 

 of the pharynx and the external branch of the laryngeal nerve. It distributes numerous branches 

 to the upper part of the gland, anastomosing with its fellow of the opposite side and with the 

 inferior thyroid arteries. The terminal branches supplying the gland are generally two in 

 number; one, the largest, the anterior branch (ramus anterior), descends at the anterior border 

 of the lateral lobe of the gland, reaches the upper border of the isthmus, and then passes in the 

 substance of the isthmus to the middle line of the neck, where it anastomoses with the corre- 

 sponding artery of the opposite side; the posterior branch (ramus posterior) descends along 



'Med.-Chir. Trans., Ixi, 229. 



2 The Treatment of Certain Malignant Growths. 



