162 COGSWELL ON THE HUMAN TEETH. 



Chemical analyses give the following as one result taking the 



incisors of man. In one hundred parts — 



Cementum. Dentine. Enambi.. 



Organic Matter— 29.27 28.70 3.59 

 Earthy Matter— 70.73 71.30 96.41 



100.00 100.00 100.00 

 These differ, however, as to the result occasionally, according 

 to the organic constituents, and as the teeth have been divided into 

 six degrees of density in man, this difference is owing whollv to the 

 presence of earthy matter. Thus in children who have been sick-- 

 ly and delicate, fed on improper unwholesome diet, a deficiency of 

 the bone forming material given in the food, and in those who also 

 inherit weak animal constitutions, from either or both parents, 

 may be found teeth of the poorest organization, chemically deficient 

 of the average earthly matter, the enamel varying little aboA'€ den- 

 tine, enamel roots imperfectly formed, and a chalky calcareous 

 appearance readily acted upon by the vitiated saliva of the mouth 

 and chemical acids ; these vehicles dissolve and destroy the organic 

 material, leaving only the gelatinous portions of the teeth to gra- 

 dually waste away : whereas, if the enamel was perfectly formed, it 

 would resist these chemical changes, and subserve the purpose of 

 the Creator for all the wants of our physical organization. 



In comparing in ordinary bone the earthy matter, inorganic, or 

 phosphate of lime so familiarly known as bone earth, we find 

 it constitutes only 54 parts of the 100, while in the enamel of th<' 

 human teeth, it is nearly 90 in the 100 parts, the enamel being 

 almost a mineral in substance, having only 3j§ parts of animal mat- 

 ter in the 100. 



If for experiment we collect the several classes of human teeth 

 from that of the lowest per centage of inorganic material, calling 

 that No. 6, and ranging up to No. 1 the most perfect and dense 

 enamel 96 per cent of lime, place these in sulphuric acid and 

 water, equal parts, the result will prove after 24 hours which class 

 of teeth will resist the acid the longest, and in propoition to the 

 density of the enamel, so the dissolving of kme salts, leaving as the 

 result, the entire loss of the enamel, forming a white sediment, 



