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PULP in the centre is the formative organ of the dentine. The 
dentine of different classes of the Vertebratce differs in its structure 
in several important particulars. It has been classified into three 
groups. (1). Hard or Uni-vascular dentine, (2). Plici-dentine, 
and (3), Vaso-dentine. 
The third substance of which teeth are formed is named 
Cementum. In man and the Carnivora it is confined to the roots 
of the teeth. In chemical composition it is nearly allied to bone. 
The Attachment of Teeth. The methods by which teeth are 
attached offer many points of interest. There are three distinct 
methods by which this is effected, 1st, Membrane, 2nd, Hinge, 
3rd, Anchylosis, 4th, Socket. 
In the first method the teeth are affixed to a fibrous membrane 
which glides over the jaw, asin the shark, which during its life has 
an enormous number of teeth. The pike and hake afford us ex- 
amples of the attachment of the teeth to the jaw-bone by hinges. 
The third method (anchylosis) may be found in the python and 
haddock, while in man and the mammalia generally they are 
inserted in a socket. 
The author then touched on the development of teeth in the 
human subject, and next pointed out how intimately the form 
and structure of the teeth were associated in different animals 
with the food and habits of life of the animal to which they 
belonged. The incisors for instance distinguish the Rodents, 
the large development of the canines the Carnivora, and a 
peculiar shape of the molars is characteristic of the Ruminants, 
