SHUFELDT.] *  OSTEOLOGY OF THE SPEOTYTO. 619 
tibia at about the junction of middle and distal thirds, thcugh it may 
_be traced after this as far as the middle of the outer condy le, where it 
terminates by a minute tubercle. The head is notched externally, near 
the centre, and has lodged at that point a small sesamoid that is in the 
lateral ligamentof the knee- joint. Posteriorly on the shaft, about midway 
down the superior tibio-fibular anchylosis, we observe a small tubercle 
for the insertion of the tendon of the biceps. The long segment that 
exists between the tibia and the phalanges of the pelvic limb is the bone 
tarso-metatarsus, or the confluent metatarsals of the second, third, and 
fourth toes with certain tarsal bones at its proximal extremity. It meas: 
ures down the anterior aspect, mesially, 4.6 centimetres, and has its ex- 
tremities enlarged for articular purposes,in common with other long bones 
ofthe skeleton. At its proximal end the bone presents superiorly two con- 
cave articular surfaces for the condyles of the tibia. They appear nearly 
on a level with each other, the bone being held vertically. The inner and 
larger of the two is elliptical in outline, antero-posteriorly; the outer and 
smaller is fashioned off behind by a tuberous process, directed upwards 
and outwards. Between these two surfaces arises a prominent tuber- 
osity, that in the articulated limb enters the intercondyloid notch of the 
tibia quite accurately, and is intended for a hgamentous attachment. An- 
teriorly and internally a groove exists that runs down the shaft, to dis- 
appear a little above its middle. This canal is deepest immediately be- 
low the articular expansion, and is here bridged over by a little arch of 
bone, a millimetre in width, that serves to bind down and hold in its 
proper place the tendon of the long extensor of the toes. Posteriorly 
there is a much deeper and longer tendinal canal, that extends the entire 
length of the shaft, being shallowest at the middle and most capacious 
at the proximal extremity; this is bounded above and internally for a 
short distance below the head of the bone by the calcaneal process, a 
thin lamina of bone that has a foramen near its base; this process is 
surmounted by an elliptical and compressed tuberosity, placed vertically. 
The opposite wall, above, of this groove is also thin, and extends, in 
common with the calcaneal process, directly backwards. There are two 
other foramina seen at this end of the tarso-matatarsus ; one just at the 
external termination of the bony bridge mentioned above, and the other 
outside and a little above it. Their pesterior openings are immediately 
behind the anterior ones, or, in other words, they do not pierce the shaft 
in any way obliquely. The shaft of this bone is nearly square on sec- 
tion for the major part of its extent, being encroached upon, however, 
both before and behind, by the aforesaid tendinal grooves. The tendons, 
especially those that occupy the posterior canal, are very prone to ossi- 
fication, forming quite sizable bones in the adult, the largest of these 
being equal to the fibula in bulk, exclusive of course of the head of that 
bone, and not being as long. Returnin g to the tarso-metatarsus, we find 
at its distal extremity, for examination, the trochlee that articulate 
with the rear segment of all the toes except hallux. Viewing this end 
with the bases of these trochlez towards one, we find the general out- 
line made by them to be crescentic, with the horns having a tendency 
to approach each other behind. The outer trochlea is the highest and 
longest from before backwards; the other two are about on the same 
level, the inner one having a posterior and internal process, while the 
middle one is possessed of a median cleft traversing its face antero- 
posteriorly. They are sharply divided from each other by narrow slits, 
that extend up as far as the articulating part, and are continued on the 
anterior aspect of the shaft for a short way as delicate groovelets. A 
foramen is situated in the outer of these, that gives passage to the ante- 
