PULPS AND SACS OF THE HUMAN TEETH. 33 



combined twigs then ramify minutely in the true membrane 

 of the sac without sending the smallest twig into the granular 

 substance.* The dental branch, after giving off these saccular 

 twigs, divides into a number of contorted ramifications between 

 the base of the pulp and the sac, which from smaller ramusculi 

 are transmitted into the pulp itself. In the case of the molars, 

 the main branches divide into three secondary branches, one 

 for each of the secondary bases. From these, three sets of 

 saccular twigs, and three packets of contorted pulp-vessels, 

 take their origin. 



While these changes have been taking place in the sacs of 

 the milk-teeth, the follicle of the first permanent molar closes, 

 and granular matter is deposited in its sac. The walls of that 

 portion of the secondary groove below it do not adhere ; the 

 edges alone do so. There is, therefore, a cavity of considerable 

 size below the sac of this tooth, or between it and the surface 



* Mr. Fox (Natural History of the Human Teeth, p. 20) and Mr. Bell 

 (Anatomy of the Teeth, p. 54, and in a note, p. 39, vol. ii. Palmer's edition of 

 Hunter's Works) have both misunderstood the statements of Mr. Hunter and 

 Dr. Blake on the relative vascularity of the membranes of the tooth-sacs. 

 (Hunter's Natural History, p. 84, and Blake, p. 4.) What Blake denominates 

 the internal lamella is the enamel pulp of Hunter, Purkinje, and Easchkow, 

 the gelatinous granular substance described in the text. He, with great 

 accuracy states that it is "more tender and delicate, and seems to contain no 

 vessels capable of conveying red blood." Under the denomination "external 

 lamella " he includes the proper vascular mucous membrane of the sac, and the 

 external spongy submucous tissue. In his search after the germs of the per- 

 manent teeth, Blake's attention appears to have been directed to the tooth-sacs 

 when in the condition he describes. Mr. Hunter, again, who had a most 

 correct conception of the constitution of the sacs, has, with his usual sagacity, 

 not confounded the granular body, or, as he denominates it, "another pulpy 

 substance," with the proper membranes of the sacs. Accordingly, in his 

 account of the relative vascularity of the membranes of the sacs, he, when 

 describing the manner in which a tooth is formed, has taken no notice of the 

 pulpy substance. Dr. Blake describes the membranes of the sacs at an early 

 period ; Mr. Hunter, again, in a child at birth, at which time the external 

 membrane is not very vascular, and has assumed somewhat of the appearance 

 of a fibro-cartilage. 



D 



