174 DENDRODUS. 



more frequently from the sides of the lateral branches, than from 

 their terminal dilatations. 



The peripheral extremities, also, of the medullary rays, and of 

 such of their subdivisions or branches as are nearest to and directed 

 towards the margin of the section, and consequently to the periphery 

 of the tooth, are resolved into fasciculi of calcigerous tubes, which 

 diverge in graceful curves from their point of origin : two of these 

 peripheral lobes are figured at PL 62 b, fig. 4. The middle tubes are 

 continued from the interspace of the diverging ones to the periphery 

 of the tooth in a line parallel with that of the main medullary canal 

 {a), which radiates from the central reticulation : the lateral tubes 

 gradually diverge more and more from this line, and those which 

 proceed from the sides of the extremity of the medullary canal run 

 at right angles to its course. The lateral tubes terminate, together 

 with those of the adjoining medullary canal, in a linear series of cal- 

 cigerous cells ; which line is continued inwards from the periphery 

 of the tooth, like a process of the external capsule, inclosing and 

 defining, as it were, each of these terminal square lobes or systems 

 of calcigerous tubes. There is a sUght indentation of the periphery of 

 the transverse section at the line of the above described inflection of 

 the cellular structure ; and this indentation (&) is a section of one of 

 the fine superficial longitudinal striae already mentioned. The in- 

 flected line of minute cells may be traced, in most parts of both sections, 

 to near the central reticulate system of medullary canals, sending off 

 branches on each side, which bound in a similar manner the diffe- 

 rent lobes of dentine, or systems of radiated calcigerous tubes which 

 are given off from the sides of the straight medullary canals. The 

 external longitudinal fine grooves on the superficies of the tooth indi- 

 cate, as above stated, the entering lines of the fine cellular cement, or 

 the interspaces of the lobes of the dentine appended to the medullary 

 canals which radiate from the central pulp-cavity or net-work. 



The medullary rays, though for the convenience of description 

 they have been termed canals — as they appear to be in the transverse 

 section of the tooth, yet are not cylindrical tubes. For it must be 

 obvious from the similarity of the structure of the two sections here 

 described from nearly the two opposite extremities of the tooth, that 



