712 MR. T. MAIfNEBS-SMITH ON THE [DcC. 4, 



Sacral Plexus. 



The nerves entering into this plexus are a large part of the first 

 lumbar, the whole of the second lumbar, and the whole of the first 

 sacral. Portion derived from lumbar nerves divides into two 

 branches ; the first sacral also divides into two branches. One of 

 the branches from lumbar part of plexus fuses with one of the 

 branches from sacral part of plexus and forms the peroneal nerve ; 

 this, as it passes down the leg, divides into two branches, which 

 seem to represent peroneal and external plantar. Peroneal divides 

 into a muscular branch passing to muscles mentioned in text and 

 a cutaneous branch to the dorsum. The external plantar divides 

 into a cutaneous branch to outer side of foot, and supplies certain 

 muscles of the sole. The remaining branch from lumbar part of 

 plexus unites with remaining branch from sacral part, and forms 

 the internal popliteal nerve ; this divides into three branches : 

 two lateral, to the inner and outer heads of the gastrocnemius ; 

 one to outer head supplying flexor longus digitorum in addition ; 

 one to inner head supplying soleus and tibialis posticus. The 

 continuation of the trunk passes down and becomes the internal 

 plantar, which is mainly cutaneous. 



A Note on the Arteeiai. System. 



The arch of the aorta has the usual mammalian arrangement, 

 turning to the left side. It gives off the three large cervical and 

 brachial branches in the usual order, viz. innominate, left carotid, 

 left subclavian. 



The trunk aorta passes down to the nineteenth vertebra (last 

 lumbar), where it ends by dividing in a peculiar tree-like manner 

 into three small and exceedingly short trunks on each side and a 

 median caudal continuation of the vessel itself — thus there are 

 seven trunks in all. 



Passing from without inwards, the outermost of the three 

 trunks divides almost immediately into the following branches : — 

 A small outermost branch for the region of the crest of the 

 ilium. A large branch which passes beneath the psoas parvus 

 and divides here into three branches, which, running down parallel 

 to each other, are all distributed to the deep part of the front of 

 the thigh, as seen in the diagram. A fairly large branch which soon 

 divides into three, two passing to the superficial part of the front 

 of the thigh, the remaining branch to the abdominal wall. These 

 arteries pass over the psoas parvus ; they may represent superficial 

 femoral and epigastric. The last branch from the outermost 

 trunk is a vessel which is partly distributed to abdominal wall and 

 also gives off branches which descend into pelvis, together with 

 two obturator arteries — large and small. 



The second trunk division of the abdominal aorta : this 2nd 

 division corresponds in its distribution with Hyrtl's ' internal iliac, 



* Penjfscbriften Wiener Akademie, Bd. T, 



