J. Playfair McMurrich 



73 



of the triceps surge, (2) the tendon of the plantaris and (3) the plantar 

 aponeurosis of the foot, a portion of it (4), however, remaining included 

 with the deep laj'er in the tendons of the flexores fibularis and tibialis. 

 It is this fourth portion of the superficial layer which gives origin to 

 the flexor brevis digitorum in those forms in which that muscle arises 

 from the tendons of the long flexors. 



The homologies of the crural muscles traced out in the preceding 

 pages may be tabulated thus : 



Amphibia. 

 Plantaris sup. medialis. 



Plantaris suji. lateralis. 



Plantaris prof. III. 

 Plantaiis prof. II. 



Plantaris prof. I. 

 Interosseus. 



Lacertilia. 

 Plantaris sup. medialis. 

 ('Plantaris sup. lateralis. 



I 



-] Plantaris sup. accessorius. 



I Plantaris sup. teniiis. 



Opossum. 



Gastrocnemius medialis. 

 Gastrocnemius lateralis 

 (less included soleus). 

 Plantaris. 



I Plantaris prof. III-II. 



Plantaris prof. I. 



Plantaris prof. I access. 

 Interosseus. 



r Soleus portion of gas- 

 } troc. lat. 

 (Flexor flbularis. 

 ( Flexor tibialis. 

 I Tibialis posticus. 



Flexor accessorius. 



Pronator tibiae. 



Mammalia. 

 Gastrocnemius medialis. 

 Gastrocnemius lateralis. 



Plantaris. 



Popliteus (superficial 



portion) ? 

 Soleus. 



Flexor fibularis. 

 Flexor tibialis. 

 Tibialis posticus. 

 Flexor accessorius. 

 Popliteus (peroneo-tibial 

 portion). 



SUMMAEY. 



1. In the crus of the urodelous amphibia the flexor muscles are ar- 

 ranged in five layers, the superficial one arising in the femoral region, 

 the others, which have a more or less oblique direction, taking their 

 origin from the fibula and slightly from the tarsus. They are inserted 

 for the most part into the plantar aponeurosis, only the deepest layer 

 inserting into the tibia. Between the second and third layers is a slen- 

 der longitudinal muscle extending between the fibula and the tarsus. 



2. The nerves of the flexor muscles of the amphibian crus are arranged 

 in two main trunks, a ramus superficialis and a ramus profundus. The 

 latter is continued into the pes as the internal plantar nerve. The former 

 divides into rami mediales which are confined to the crus and a ramus 

 fibularis which is continued into the pes as the external plantar nerve. 

 The rami superficiales mediales supply the first, second and third layers 

 of muscles, the ramiTS superficialis fibularis, the fibulo-tarsalis and the 

 ramus profundus the fourth and fifth layers. 



3. A complete separation of the prseaxial and postaxial nerve fibers does 

 not take place at tlie knee-joint in the amphibia, but the ramus pro- 

 fundus for a considerable portion of its course contains fibers which are 

 distributed to the prgeaxial surface of the crus. 



4. In the lacertilian crus the same muscle layers that occur in the 



