DISSECTION OF THE LOWKK KXTKKM1TY 163 



(a) Short extensor of great toe (M. extensor hallucis brevis). 



(b) Short extensor of digits (M. extensor digitorum brevis). 



Determine the relation of these muscles to the tendons of the 

 long extensor of the digits. What is their action? Have they 

 homologues in the hand? 



(c) Dorsal interosseous muscles (Mm. inter ossei dor sales). 



Compare these with similar muscles found in the hand, as 

 regards origin, insertion, action, etc. 



Where are the bursae intermetatarsophalangeae situated? 



LATERAL OR PERONEAL REGION OF LEG (RE GIG 

 CRURIS LATERALI8). 



The superficial fascia of this region has already been studied. 

 An anterior intermuscular septum (septum inter muscular e ante- 

 rius [fibulare] ) has been found passing from the deep fascia into 

 the crista anterior fibulae. Incise the deep fascia longitudinally 

 in this region ; reflect it posteriorly and note the corresponding 

 posterior [fibular] intermuscular septum (septum intermuscu- 

 lar e posterius [fibulare] ) going to the crista lateralis fibulae. A 

 lateral or peroneal osteofascial compartment is thus formed. 

 Dissect its contents and supplement the dissection by the use of 

 cross-sections made at different levels ; note carefully the altera- 

 tions in the relations of the different contents of the compart- 

 ment at different levels. Study the following : 



Peroneal Muscles and Retinacula. 



Clean each muscle carefully, defining well its borders and 

 noting the form, position, origin, insertion, action, and innerva- 

 tion of each. 



(a) Long peroneal muscle (M. peronaeus longus). What action does this 



muscle have as regards the arch of the foot? 



(b) Short peroneal muscle (M. peronaeus brevis). 



Trace the tendons of both muscles distalward into the foot. 

 What are their relative positions in the fossa retromalleolaris 

 lateralis? (Cf. Fig. 68.) What is the trochlear process (j,n- 

 cessus trochlearis) of the os calcis? Examine the bony foot and 

 determine the position of the peroneal sulcus (sulcti* M. peronai '> 

 [longi]). 



Define next the retaining bands of the peroneal muscles 

 macula}. (Cf. Spalteholz's Atlas, Fig. 409.) 



