50 



THE BONES AND JOINTS. 



Fig. 45- 



Tibio-fibula of Rana escii- 

 lenta, twice nat. size, seen 

 from below. 



a a Grooves. 



/ Foramen nutritium. 



t Anterior artici'lar ex- 

 tremity. 



/' Posterior articular ex- 

 tremity. 



I" Groove on malleolus in- 

 ternus for tendon of 

 111. tibialis posticus. 



from above dowaiwards. On the upper as also 

 oil the lower surface of the bone is a groove^ 

 passing" from the middle towards each ex- 

 tremity ; this deepens as it proceeds, and is an 

 indication of the compound natm'e of the bone. 

 In the middle of each surface of the bone 

 is the opening of a canal, through which a 

 bristle may be passed : the canal has bony 

 walls. The medullary cavity is, for the most 

 part, double, being single only in the middle. 

 The anterior extremity is articular, and presents 

 a median groove, which is prolonged on to the 

 under surface. The posterior extremity forms 

 a transverse condyle, which has at its inner 

 part a notch for the tendon of the m. tibialis 

 posticus. 



The knee-joint consists of a capsule strength- 

 ened by the insertions of numerous tendons. 

 Within this the articular surfaces 

 of the femur and tibio-fibula are 

 connected by means of fibro-elas- 

 tic bands, which spring from the 

 latter bone and cross each other, 

 thus representing the lig. cruciata. 

 The articular surfaces are more- 

 over deepened by loose semilunar 

 cartilages, corresponding with 

 the inter-articular cartilages of 

 the knee-joint of man. In addi- 

 tion, on either side of the joint, 

 are found auxiliary ligaments. 



Fig. 46. 



Section of the tibio- 

 fibula through tlie 

 under extremity. 



a Cartilaginous 

 ejnphysis. 



m Marrow cavities. 



I" Connecting 

 mass. 



1 1' The two cylin- 

 ders of bone. 



3. The foot (Fig. 47). 



a. The ankle, ossa tarsi. The tarsus consists of two rows of 

 bones. 



a. The proximal row consists of two long tubular bones (Fig. 

 47 ac), which are parallel ^ to each other, and imdoubtedly cor- 

 respond with the astragalus [talus) and calcaneum. The bones 

 are separated in the middle, but approach each other at either end. 

 The outer of these bones {c) I have named calcaneum, following 

 Cuvier and Dugès ; the inner, astragalus {ci). The two bones are 



