258 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



fully furnished, and by five the whole of the incisors are in full wear, 

 and indicate the extent to which they have been worn proportionate to 

 the period since their eruption. The central incisors then appear as 

 shown in b, Pig. 101, B, whereas the corner teeth, having just protruded, 

 are shelly, as shown in a. 



At six the central incisors lose their mark ; at seven this occurs 

 with the middle one, and at eight all the infundibula are worn out, and 

 the plate of the tooth is clean and only very slightly marked in the 

 corner teeth. Beyond this period the horse is stated to be aged. The 

 incisors protrude straighter from the receding jaw; the teeth become 



narrower, and their wearing surface becomes 

 triangular, as seen at c, d, and e, Fig. 101, B. 

 This distinguishes the old animal. 



The table on the preceding page, taken 

 from the " Encyolopadie cler gessammten 

 Thi^rheilkunde," indicates the wear of the in- 

 cisors of the horse at different ages (Fig. 102). 

 Dentition in the Ox. — The incisor teeth of 

 the lower jaw of the ox are simple, and eight 

 in number (Fig. 103). From the periods of 

 eruption of both temporary and permanent 

 teeth being regular, the latter being much 

 the broader, the age of the animal is readily 

 determined. Further, the sharp teeth become 

 more and more blunt and narrow, until in old 

 cattle they are reduced to very small stumps. 

 The wear of the incisors commences on. the free border, both in the decid- 

 uous and permanent teeth, the enamel being worn gradually from the 

 table of the tooth, from the anterior border posteriorly, the dentine being- 

 exposed in zigzag lines, which at the sides extend further toward the 

 neck of the teeth than in the middle. When the enamel is all gone from 

 the table of the incisors (after the tenth year), the entire crowns of the 

 teeth wear 'down until, in extreme age, only the necks are left. The 

 following table gives the succession of changes in the ox : — 



Fig. 103.— Longitudinal Sec- 

 tion of Incisor Tooth of 

 Ruminant. (Ellenherijer.) 



C, trioth-eavity ; G, enamel : E, pulp-canal ; 

 D, dentine. 



SlMONDS. 



Table of Eaely Average 

 (Improved Breeds). 



.SlMONDS. 



Table of Late Average 

 (Improved Breeds). 



GlRARD. 



Table of- Late Average 

 (Unimproved Breeds). 





W3 



o 



No. of Teeth. 



u 



2 

 2 

 o 

 3 







3 

 9 

 3 



!) 



No. of Teeth. 



i 



c No. of Teeth. 



1 



2 

 2 

 3 



9 

 3 

 9 

 3 



2 permanent incisors 



6 



8 



2 permanent incisors 

 4 



6 



8 



2 

 3 

 4 

 5 



3 2 permanent incisors 



4 



|6 



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