TEETH. 243 



paid great attention to the subject, informs us that these spongy 

 portions of bones are composed of, 



Earthy salts, . 60 



Cartilage, . 30 



Fatty matter, . 10 



100-* 



The blood-vessels and several membranes of the body some- 

 times ossify. In such cases it would appear from the analysis of 

 an ossified pericardium by Petroz and Robinet, that, instead of 

 cartilage, such ossifications have an albuminous membrane much 

 smaller in quantity than the cartilage of real bones. The result 

 of their analysis was as follows : 



Animal membrane, gelatin, and albumen, 24-2 

 Common salt and sulphate of soda, . 4O 

 Carbonate of lime, . . 6*5 



Phosphate of lime, . . . 65*3 



lOO'-Of 



CHAPTER II. 



OF TEETH. 



THOUGH the teeth are in fact bones, yet, as they contain some 

 substances which do not occur in any other part of the bony 

 structure, they deserve to be described in a separate chapter. 



The human teeth in an adult individual amount to 32 ; 

 16 being set in each jaw. There are 4 incisors or cutting teeth 

 in each jaw, placed in the fore-part of the mouth, forming the 

 convex prominent part of the dental arch. They are wedge- 

 shaped ; being intended, as the name implies, for cutting the food, 

 that only the quantity capable of being masticated may be taken 

 into the mouth at once. 



There are two canine teeth in each jaw, one on each side of the 

 incisors. They have a single root like the cutting teeth, but 

 longer, and their crown terminates in a blunt point. 



The bicuspid teeth or smaller molars are four in number in 



*~Journ. de Pliarmacie, xv. 23C. f Ibid. ix. 507. 



