156 ANATOMY AND PHYSIOLOGY. 



the chemical structure of bone, detailed before, it will be under- 

 stood how the teeth are pained when anything hot or acid is taken 

 into the mouth ; why the patient who is to use acid drops is always 

 directed to suck them through a quill, that they may not come into 

 contact with the teeth, and how the teeth blacken, and are actually 

 dissolved away in persons who are subject to acidity of the stomach. 

 When a hole has formed in a tooth, no pain is felt till the cavity is 

 reached, and the nerve exposed, and then, as almost every one 

 knows by experience, the pain is most excruciating. Sometimes 

 it is relieved by some powerful stimulant dropped into the tooth, as 

 the essential oil of cloves, sometimes by the recently discovered 

 substance called kreosote, which has the property of deadening the 

 nerve, and sometimes the tortured victim is glad to appease the 

 tormentor by destroying the nerve, by the introduction of a hot 

 wire. If the cavity is not large, it ought to be stopped ; an opera- 

 tion which generally succeeds in preserving the tooth for a long 

 time, by excluding the air, and all other agents which could act 

 upon it. This stopping ought to be done with gold leaf, or some- 

 thing of that kind, and by a respectable dentist ; and no one should 

 trust his teeth in the hands of an ignorant dentist. If stopping 

 the tooth does not prevent the recurrence of toothache, the offending 

 member must be removed ; and this last resource should never be 

 deferred so long that the stump requires to be dug out of the jaw; 

 because then what is a brief though painful operation, is converted 

 into one which is tedious, and often insufferable. 



The teeth at first lie deep within the jaw bones, covered, at birth, 

 by the thick gum. Their rudiments at birth are very small. The 

 crown or upper part of the tooth is formed first, then the body, then 

 the enamel is deposited on the crown, and lastly, the fangs grow as 

 the tooth becomes protruded. When the jaw of a new-born child 

 is dissected, a pulp is found for each tooth, like a little stool, into 

 which blood-vessels are seen running, on the top of which the bone 

 is deposited, and after the tooth has attained its shape, the pulpy 

 stool shrinks away almost to nothing, except the small quantity of 

 cellular tissue which conveys the vessels and nerves into the cen- 

 tral cavity. The whole tooth is enclosed within a delicate mem- 

 brane, which becomes ruptured when the tooth bursts forth. The 

 gum of an infant has a sharp line running along it, which serves it 

 to catch anything that is put into its mouth ; and this line becomes 

 broader and flattened, and finally disappears, previous to the erup- 

 tion of teeth. The order of eruption is generally the following : 



