16 



THE BONES AND JOINTS. 



acquainted with its histological peculiarities. If a long bone of the 

 frog 1 be dried, the femur for example, the middle part is found to 



differ considerably from the epi- 

 physes in colour and in other par- 

 ticulars. The shaft alone has the 

 appearance of bone, the epiphysis 

 consisting of a white, opaque, firm 

 substance, resembling plaster of 

 Paris or lime, but which in the 

 fresh moist state is exactly like 

 cartilage. The epiphyses, which 

 are fitted to the ends of the dia- 

 physis like the cap of a stick- 

 handle, have sharply defined mar- 

 gins (Fig. 3), as is well seen in 

 Figs. 36, 39, 45, and 46. If a sec- 

 tion be made through the epiphysis 

 and part of the diaphysis, the long 

 tube of true bone is seen to cease 

 abruptly above o, Fig. 3, and over 

 the end of it the epiphysis E is 

 fixed. This epiphysis consists al- 

 most entirely of calcified cartilage 

 c, and has merely a superficial 

 layer of hyaline cartilage A. The 

 bony cylinder of the diaphysis <?, which contains the marrow M in 

 its interior, is shut off from the epiphysis by hyaline cartilage, the 

 cells of which are arranged in transverse layers, o. 



Longitudinal section through the upper ex- 

 tremity of the femur of Rana etculenta, 

 magnified. 



A Hyaline cartilage (articular cartilage), 

 c Hyaline cartilage closing end of bony 



cylinder. 



c' Calcined cartilage of epiphysis. 

 D Bony cylinder of diaphysis. 

 E Epiphysis. 

 M Marrow cavity. 

 o End of diaphysis. 



I. THE VERTEBRAL COLUMN. 



The vertebral column of the frog consists of ten bones, viz. nine 

 true vertebrae, and the rod-shaped urostyle, which alone is almost as 

 long as all the remaining vertebrae. 



I. GENERAL DESCRIPTION OF THE NINE VERTEBRAE. 



a. The ladies of the vertebrae are compressed from above down- 

 wards; the posterior surface of each body, with the exception of 



