DEVELOPMENT OF ARTERIES IN FORELIMB OF PIG. 149 



Numerous investigations on the development of the limb-arteries in mammals 

 are to be found. The investigators have concerned themselves primarily with the 

 phylogenetic rise and fall of particular vascular stems in the limb. 



Zuckerkandl (1894) studied rabbit and cat embryos and also two human 

 embryos. The earliest stages seen by him showed a thick axial vessel in the limb. 

 The forearm portion forms the arteria interossea volaris. Both human embryos 

 showed the same. The volar interosseous gives off a thick dorsal branch which 

 runs between the proximal parts of the radius and ulna. Distally, it supplies a 

 branch to the volar part of the forearm, while part of the blood-stream is turned 

 dorsally and, passing through the carpus, supplies the dorsum of the hand. Leboucq 

 (1893) has described the same in the human embryo. In addition to the chief 

 stem, there is present in rabbit and cat embryos a vessel running to the volar 

 aspect along with the median nerve. Meanwhile, the volar interosseous decreases 

 in size and the arteria mediana undergoes an increase. Similarly in man, a median 

 period follows the interosseous (Janosik, 1891; De Vriese, 1902), and this is finally 

 superseded by the dominance of the ulnar and radial. 



Grosser (1901) described two bat embryos (Rinolophus hipposiderus) , one of 

 4.75 mm., one of 6.25 mm. An axial stem shows as the main trunk of the limb 

 supply. Its distal part forms the arteria interossea volaris. This divides at its 

 extremity into a feeble ventral branch, which supplies the volar aspect, and a third 

 dorsal twig, which pierces the carpal region and supplies the dorsal side of the 

 extremity. In a 7.25-mm. embryo the ramus perforans carpi dwindles and a 

 thick branch goes from the interosseous to the dorsal side between the radius and 

 ulna, proximal to the carpus. Soon afterward the arteria mediana becomes the 

 chief stem. 



Even earlier, Hochstetter (1896) showed for the Echidna the arteria interosseus 

 as the temporary chief vessel of the limb. Later, the radial takes on the role of 

 the chief blood-supply of the limb. The brachial undergoes a change by which it is 

 transformed into a capillary net. This is secondary and due to an obstruction to 

 the flow of the blood through the brachial as the result of the arrangement of 

 musculature and humerus (Goppert, 1905). 



Zuckerkandl (1907) investigated the mole, Talpa europea. Embryos 6, 8, 

 and 10 mm. long show that the ontogeny follows a quite typical path until a 

 brachialis, an interosseous, and (as a division of the latter) a mediana are formed. 

 Then begins the formation of a thick dorsal path which forces the old-stem artery 

 of the arm and forearm into the background. Here, also, the new path forms itself 

 out of numerous anastomosing vessels through quite fine twigs. Zuckerkandl 

 sees in this the formation of a more favorable path for adaptation to the particular 

 habits of the mole. 



The investigations of Miiller (1903) demand particular consideration. He 

 studied a considerable number of human embryos and found that the definitive 

 arrangement was reached in embryos from 16 to 20 mm. In the youngest stage 

 (5 mm.) the limb arteries and veins are separable by then relation to the limb mar- 

 gin. The primordium of the arterial system belongs to an axially situated net 



