BONE. . 311 



branched canals may be seen in both transverse and longitu- 

 dinal sections. (See Plate XXXV. figs. 1, 2.) 



The majority of these proceed directly from the ossified 

 part of the shaft in connection with the epiphysis ; in this 

 situation they are of larger size, and are also fewer in number, 

 than they are higher up in the epiphysis, not exceeding 

 usually five or six, but becoming multiplied, by the giving 

 off of branches, to as many as fourteen or sixteen ; others, 

 however, enter the epiphysis from the sides, near the junction 

 of the bone and cartilage. 



The interior of these canals is occupied with blood-vessels 

 and with granular nucleated cells, precisely like those ex- 

 isting in the medullary cells of bone. (See Plate XXX Y. 

 fig. 3.) 



The cartilage cells in a transverse section of the canals im- 

 mediately surrounding their orifices are disposed in a rayed 

 manner. 



Having thus described the structure, contents, and distri- 

 bution of these canals, we will next inquire their use. (See 

 Plate XXXV. fig. 3.) 



If a number of transverse sections be made not merely of 

 the cartilaginous epiphysis, but also of the bone in connection 

 with it, and if these be examined in the order of their re- 

 moval, it will be observed, first, that in those sections which 

 are made from the cartilaginous epiphysis most removed 

 from the bone, the apertures of these canals are small and 

 numerous (see Plate XXXV. fig. 1) ; second, that in the 

 sections taken from the proximal end of the epiphysis the 

 canals are fewer in number and their orifices larger (see 

 Plate XXXV.) ; thirdly, that in other slices, which include 

 a portiorn of both catilage and bone, the latter always com- 

 mences on the circumference of the section, proceeding 

 gradually inwards, the portion of cartilage surrounding the 

 canals in question being the last to become ossified (see 

 Plate XXXV. figs. 2, 3.); fourthly, in cuttings made below 

 the cartilage and through the bone, spaces four or five in 

 number, filled with granular cells corresponding in situation 

 with the afore-described canals, will be observed ; fifthly, in 



c c 



