272 



ANATOMY OF VERTEBRATES. 



somewhat narrower, but of simple form. Each division or tubercle 

 of the molar is separately developed, and they become confluent 

 in the course of growth. According to the analysis of Lassaigne, 

 99-5 parts of the dental tissue of the Ornithorhynchus have the 

 composition of horn ; this is hardened by 0-3 parts of phosphate 



of lime. 



The notice of the dental apparatus of the Monotremes ought to 



include mention of the two short and thick conical processes, fig. 



212, g, </, which project from the forepart of the raised intermolar 



portion of the tongue, in the Ornithorhynchus ; and like the more 



numerous spines on the corresponding part of the 

 tongue of the Echidna, represent, in these low- 

 organised mammals, the lingual teeth of fishes. 

 B. Bruta. The teeth of the Orycterope, or 

 Cape Ant-eater, are of a simple form, but pecu- 

 liar structure ; their common number in the 

 mature animal is --: = 26, and they all belong to 

 the molar series. The first and smallest is soon 

 lost. The proportions of the persistent teeth, 

 the depth of their sockets, and their structure, 

 as viewed in longitudinal section with the naked 



213 



212 



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f 



Tongue, lingvial teeth, 

 and larynx of the Orni- 

 thorhynchus. 



Section of lower jaw and teeth of the Orycteropus. Nat. size 



eye, are shown in fig. 213. The teeth are continued, solid, and of 

 the same dimensions, to the bottom of the socket, and terminate in 

 a truncate and undivided base. If each be viewed as an aggre- 

 gate of teeth, as partially shown in fig. 247, vol. i., p. 396, it 

 will be found that the component denticle has its base excavated 

 by a conical pulp-cavity, as in other animals, and which is persis- 

 tent, as in the rest of the order Bruta. The wide inferior aper- 

 tures of these pulp-cavities constitute the pores observable on the 

 base of the compound tooth of the Orycterope, and give to that 

 part a close resemblance to the section of a cane. The canals to 

 which these pores lead are the centres of radiation of the dentinal 



