342 The Nerves and Muscles of the Leg 
in young children the attachment to the head of the fibula is weak. In 
embryos of the third month the tendon of insertion of the biceps can be 
followed for some distance down the fibular side of the leg but there seems 
to be some attachment to the fibula. 
b. Nerve Supply. 
1. Relations of the Nerves of the Muscles of the Hamstring Group to the 
Spinal Nerves. 
In the adult it is difficult to trace back with certainty to the spinal 
nerves the nerves distributed to these muscles. In general the special 
dissections which I have made have revealed conditions which correspond 
well with the data given by G. D. Thane in Quain’s Anatomy, Vol. III, 
Part II, p. 331, which in turn are based on data derived from Pater- 
son and Hisler. According to the description there given the nerve to 
the adductor magnus arises from the 4th and 5th lumbar nerves, that of 
the semimembranosus from the 4th and 5th lumbar and 1st sacral nerves. 
The two nerves of the semitendinosus arise from the 5th lumbar and Ist 
and 2d sacral nerves. I have found the inferior nerve arising from the 
4th and 5th lumbar and 1st sacral, the superior from the 1st and 2d 
sacral nerves. The nerves for the long head of the biceps arise from the 
1st, 2d, and 3d sacral nerves ; that of the short head of the biceps from the 
5th lumbar and Ist, or Ist and 2d, sacral nerves. In Text Fig. 6 the re- 
lation of these nerves to the sciatic nerve is diagrammatically shown. A 
study of Plate III, Fig. 3, and Plate VIII, Figs. 1 and 3, will show that 
a distribution of spinal root fibres corresponding with this scheme would 
follow from the more direct paths to the muscle anlages open to fibres 
growing out from the sacral spinal nerves when the muscle anlages first 
appear. 
2. Relation of the Nerves of the Hamstring Muscles to the Sciatic Nerve. 
To the semitendinosus and to the long head of the biceps, as a rule, 
two separate nerves are given, one going to the proximal the other to 
the middle or distal third of each muscle. Occasionally each of these 
nerves may be doubled and not infrequently the nerves to each muscle 
are combined for a part of their course in a common trunk. For the 
semimembranosus and adductor magnus as a rule a single branch springs ” 
from the sciatic nerve. This branch soon divides into separate branches 
for each muscle. The various nerves mentioned spring at varying heights 
from the sciatic nerve and are variously combined in the branches which 
spring from this nerve. In Table XXV the relative origins of the 
