ARTERIES OF HUMAN LOWER EXTREMITY 61 
plates which fit after careful adjustment and to remove those 
which do not join. In this way the plexus represented in the 
reconstruction is probably less dense than that occurring in the 
embryo. The reconstruction, in fact, reproduces the spirit rather 
than the letter of the original. 
In reconstructing the stage of 6 mm. consecutive sections 
were used, and these were comparatively thick (20 »). In this 
case the parts usually fitted so accurately that the plexuses, 
as reproduced, must represent, as nearly as possible, the actual 
conditions in the original. 
c. Nomenclature 
As already noted, the term a. poplitea profunda is used in the 
following account to denote the popliteal section of the em- 
bryonic axial artery. The term a. ischiadica and a. interossea 
have been retained for the proximal distal parts of that artery, 
respectively. 
To the artery which normally perforates the tarsus of adult 
ungulates, and which has been recognized in all mammalian 
embryos hitherto observed, numerous terms have been applied.? 
The name ramus perforans tarsi is used here. 
For two of the embryonic arteries the names used by Hyrtl in 
1864 have been retained. They are the r. coronarius (of the 
medial malleolus) and the a. peronaea posterior superficialis. 
The description of a number of embryonic vessels, the existence 
of which has not been noted heretofore, has necessitated the use 
of several new terms. ‘These conform, as nearly as may be, with 
current usage. 
In referring to the relative positions of the structures of the 
limb, the adult terms of orientation have been used throughout. 
This course has been adopted in order to avoid the confusion 
which might arise from the alternative use of two sets of terms 
in making comparisons between the relative positions of struc- 
tures in the adult and embryonic limb, respectively. 
’ Ramus and sinum tarsi, Hyrtl (’64); Arteria tarsea perforans, Siissdorf 
(89); perforans tarsi, DeVriese (’92) Arteria anastomotica tarsi, Salvi (’99). 
