640 THE BLOOD-VASCULAR SYSTEM 



Cases are on record in wWch the ulnar artery, arising in the middle of the arm passes behind 

 the medial epicondjde to follow the nerve in the forearm as usual. The ulnar artery here 

 replaces the superior ulnar collateral and the ulnar recurrent. This anomaly is explained in a 

 striking way by the account given by de Vriese of the development of the vessels of the upper 

 extremity. 



Several important variations in the distribution of the main vessels belong to the second 

 category. It is not uncommon for hvo arteries to arise from the primitive peri-median plexus 

 of the arm. In such cases one artery usually takes a course dorsal to the median nerve, i. e., 

 it is crossed medio-laterally by the medial head of the nerve and in the contrary direction by 

 the nerve itself. Its course con-esponds to that taken by the ordinary axillo-brachial trunk; 

 it is known as the deep brachial artery. The other vessel takes a course ventral to the median, 

 nerve, and is known as the superficial brachial. The superficial brachial may join its com- 

 panion artery, at or above the elbow, or one of the forearm vessels arising from it. In either 

 case the superficial brachial is referred to as a "vas aberrans." Pei'sistence of the superficial 

 brachial further operates as a frequent cause of abnormality in the forearm in that it is often 

 continued directly into one or more of the chief arteries of the latter, the deep brachial taking 

 the remainder. This condition is classified as a high origin of the radial, ulnar, etc., as the case 

 may be. 



There is another type of variation belonging to the same category. In this, one large 

 artery only occurs above the elbow which, instead of following the normal course of the brachial, 

 passes, entirely or in part, ventral to the median nerve. In the first case this vessel represents 

 the superficial brachial, the deep being absent. In the second it corresponds in its upper part 

 to the deep brachial and in its lower to the superficial, the two components varying in inverse 

 proportion. 



E. Miiller*, who has made a study of the variations belonging to this category, classifies 

 the abnormal artery occurring in cases of vas aberrans, of high origin of forearm-vessels, and 

 of single abnormal brachial, according to the proportion of superficial brachial present in 

 any particular example, as a. brachialis superficialis superior media, inferior, or ima. In an 

 embryo of 11.7 milUmetres he found a system of arterial channels in relation with the median 

 nerve out of which any variation of this category might have been produced during further 

 development. 



In cases in which the superficial brachial alone persists, the branches of the axillary (and 

 sometimes the profunda brachii and superior ulnar collateral) arise from a common (deep 

 brachial) trunk called the profunda axillaris. In cases in which the deep and superficial brachial 

 co-exist examples of continuation of the superficial brachial into the radial are rather common, 

 continuation into the ulnar less so. Continuation of the superficial brachial into the median, 

 interosseous, or of posterior interosseous arteries occasionally occur, but they are rare. In any 

 case of high origin a cross branch may connect the high vessel with the deep brachial in the 

 neighbourhood of the elbow. The ulnar artery when arising high is often superficial to the 

 forearm flexors (a fact which has not been explained on embryological grounds), the inter- 

 osseous arising from the radial. 



The variations occurring in the arteries of the lower extremity are usually compensatory, 

 or due to persistence of alternative embryonic channels. The sciatic (inferior gluteal) very 

 rarely persists as the main artery of supply. In such cases the small femoral ends as the genu 

 suprema which then appears to be a branch of the profunda. 



The profunda is irregular; its origin may occur anywhere between the inguinal ligament 

 and a point four inches below it. The median or lateral circumflex may arise from the femoral. 

 The branches of the latter commonly .arise separately from the profunda, or from the femoral. 

 The popliteal does not vary much in its point of division. High division is commoner than low, 

 but is never higher than the lower epiphyseal Une of the femur. 



The anterior tibial may be small and only reach the middle or lower part of the leg. In 

 such cases an enlarged anterior peroneal may end as the dorsalis pedis, or the dorsal metatarsal 

 arteries may be suppHed from the plantar arch. Cases in which the anterior peroneal supplies 

 the dorsum of the foot do not represent a direct inheritance of the embryonic method by which 

 the peroneal artery performs this office. The embryonic route of the peroneal to the dorsum 

 of the foot is transtarsal. The anterior tibial artery may reach the extensor surface of the leg by 

 accompanying the peroneal nerve. This case, Uke that of the ulnar artery passing around the 

 medial epicondyle, is interesting in connection with the work of de Vriese. 



The posterior tibial artery may be absent or small, the peroneal replacing it, or reinforcing 

 it by means of the ramus communicans. Absence of the peroneal has been recorded by Otto 

 and W. Krause, but these cases are explained by Barkow as being suppression of the posterior 

 tibial artery between the origin of the peroneal and the communicating branch (Quain). 



The lateral plantar is sometimes very small, in which case the plantar arch may be supplied 

 by a large deep plantar. In rare cases there is a superficial plantar arch as in the embryo. 



3. THE SYSTEMIC VEINS 



The systemic veins ;iro natur:illy divided into tliree groups — (1) the veins of 

 the heart; (2) the vena cava superior and its tributaries, namely the veins of the 

 head, neck, upper extremity, and thorax; and (3) the vena cava inferior and its 

 tributaries, namely, the portal system, and the veins of the abdomen, pelvis, and 

 lower extrcMnity. 



* E. Miiller, Anat. Hefte, No. 22, 1903. 



