118 ANIMAL DKX'I'ISTRV. 



same precocity will he observed in the sheddini;- of the tem- 

 porary teeth, from the increased amount of hard food in- 

 gested at an age when the teeth are still defective in tex- 

 ture. In the one-year-old race horse that is trained and 

 fed to force the development of the muscular system the 

 teeth will share in the development providing the unnatural 

 requirement does not impair the general health. 



(2) The texture of the teeth varies in difTerent animals 

 of the same class reared under the same conditions, from 

 causes too obscure to recognize. Deficiency in the inorganic 

 proximate principles of food in certain districts has been 

 observed to yield horses with soft teeth. The variation in 

 the texture of the teeth will either hasten or retard the 

 retrogression of the teeth. AMicn the teeth arc hard the 

 events by which age is determined will be retarded, and as 

 a consequence the animal will appear young. When the 

 teeth are soft the reverse occurs and the animal appears 

 older. The anomalies caused by the varied density of the 

 tooth substance are precocious or retarded changes in the 

 cups, infundibula, shape of the tables and length of the 

 crowns. One of the most pronounced results of soft teeth 

 is the shortening instead of elongation of the incisor crowns 

 as the animal becomes old. 



(3) The infundibula of the incisor teeth may vary 

 greatly as to their depth. They may be very shallow in 

 some animals and very deep in others, and thus prove mis- 

 leading when depended upon alone in the determination of 

 age. 



(4) The cups of the infundibula are equally subject to 

 variations, due to the amount of crusta petrosa in the bot- 

 tom of the infundibula. In some teeth the infundibula are 

 almost full of crusta petrosa, while others contain but a 

 small amount. When full the cup disappears early, and 

 when empty it persists longer. This anomaly is not con- 



