104 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



The internal maxillary and the superficial temporal arteries formBi 

 the two terminal branches of the external carotid artery. The] 

 former passes in the direction of the orbit and gives ofif the inferior 

 alveola branch to the mandible ; the latter passes to the temporal 

 region and gives off the transverse facial artery to the cheek and 

 face. 



To simplify the presentation of differences found, it is conven- 

 ient to use the following captions : 



The Internal Carotid-Occipital differences — A common difference 

 in the relationships just noted is a condition where the internal 

 carotid artery and the occipital branch arise from the common 

 carotid as a single trunk, the innominate (figures 2, 3, 7 and 12 IN.), 

 which subsequently divides. Interesting gradations in respect to 

 the division are found, from the condition (figure 8) where the 

 two arteries arise separately from the common carotid artery, and 

 where there is no innominate formed, to that where a long innomi- 

 nate is formed as shown in figure 7. The order of the division is 

 of interest also since in some cases (figure 2), the occipital branch 

 is morphologically the most posterior, in others (figures 9 and 12). 

 the internal carotid artery occupies such a position. In the first 

 condition there is no crossing of the two, the occipital passes dorsad 

 to the muscles of the head and neck, and the internal carotid artery 

 passes directly mesad under the auditory bulla. In the second 

 condition, there is a crossing, the occipital branch usually passing 

 laterad of the deeper lying internal carotid trunk, although here 

 again there seems to be some variability, since in one case (figure 

 4) the opposite is the case. 



The External Maxillary-Lingual differences — While there has 

 been noted no case where the sequential order in which these two 

 arteries are given off from the external carotid artery, the relative 

 differences in distances from one another in their origin is worthy 

 of study. In two individuals (figures 6 and 7) the interval be- 

 tween the two is very considerable, being very nearly a centimeter. 

 From this extreme gradations occur, the distance between their 

 points of origin on the carotid gradually approximating one another 

 as is shown in figures 3, 2 and 5 respectively. Finally there is 

 formed in some cases, a common trunk, an innominate, before the 

 division takes place, as shown in figures 4, 9 and 12. It is apparent 

 that this approximation may take place in either direction, that is, 

 the lingual may move cephalad to effect the junction with the max- 

 illary, as shown in figure 9, or the maxillary may move caudad as 

 represented in figure 4. In the condition shown in figure 5, both 



