OSTEOLOGY 171 



tarsal bones. It is deeply grooved upon its plantar surface 

 for the passage of the peroneus longus. In addition to the 

 calcaneum, it articulates with the scaphoid, ectocuneiform 

 and the fourth and fifth metatarsals. 



Immediately distad of the astragalus is the scaphoid, 

 considerably broader dorsad than ventrad. This articulates 

 with all the bones of the tarsus save the calcaneum, and 

 from it the abductor hallucis originates. It is as broad as 

 both the ecto- and mesocuneiforms together. 



The ectocuneiform is the connecting link between the 

 scaphoid and third metatarsal, and is of the same width as 

 the latter. Upon its plantar surface is inserted the tendon 

 of the peroneus longus, and from it originate one head of the 

 flexor hallucis brevis and the adductor digiti secundi. 



The mesocuneiform is smaller than the last, but occupies 

 an analogous position between the scaphoid and the second 

 metatarsal. 



The entocuneiform is the most medial one of the cunei- 

 forms and the longest, lying mediad to the scaphoid, meso- 

 cuneiform and a portion of metatarsal one. It also artic- 

 ulates with the tarsal sesamoid bone. Upon it is inserted 

 the tendon of the tibialis anticus, and from it arise one head 

 of the flexor hallucis brevis and adductor digiti quarti. 



Metatarsus. The first metatarsal is much the shortest, 

 and about two-thirds as broad as the widest, w^hich is the 

 second. The fifth extends far proximad to laterad and 

 ventrad of the tarsus, in the form of the peroneal process, 

 upon which is inserted the peroneus brevis. Measuring the 

 visible length of each metatarsal along its dorsum, and 

 taking the length of the longest, which is the fifth, as repre- 

 senting 100, we get the following approximate values for the 

 four others. In Homodontomys the first is 53; the second 

 and third 88; and the fourth 94. In Neotoma the first is 54; 

 the second 91 ; the third 94; and the fourth 93. In Teonoma 

 the first is 57; the second 87; the third 96; and the fourth 95. 

 There is, of course, some individual variation in this respect. 



