426 



DIGESTIVE SYSTEM OF THE DOG 



end or at both ends of the series.^ The first tooth appears only once. The fourth 

 tooth of the upi:)er row and the fifth of the lower row are much larger than the rest, 

 and termed sectorial or carnassial teeth. From these the teeth diminish in size 

 both forward and l)ackward. The upper and lower teeth do not correspond, but 

 rather dovetail. The teeth behind the sectorial ones are tuberculate, i. e., have 

 rounded eminences on the masticatory surface. The others are all sectorial in 

 character, i. <?., have sharp-edged, pointed projections, the middle one being the 

 most prominent. The premolars are laterally compressed, and are separated by 

 intervals from the canines and from each other, except in the brachycephalic 

 breeds. The upper molars have wide, somewhat quadrangular crowns, and three 

 roots. The crown of the upper fourth premolar (Dens sectorius) is divided into 

 two pointed lobes and has an antero-internal tubercle; it has three roots. The 



Fig. 329. — Dissection ok Hkah of Doc, Showing Salivary Glands, etc. 

 a. Ocular muscles; b, pterygoideus internus (cut); c, stylo-glossus; rf, digastricus (cut); e, genio-glossus; 

 /, genio-hyoideus; g, hyo-glossus; h, thyro-pharyngeus; /, crico-pharyiigeus; A;, thyro-hyoideus; I, zygomatic 

 process of temporal (sawn off); 1, parotid gland; 2, submaxillary gland; 3, posterior part of sublingual gland; 

 3', anterior part of same; 4< submaxillary duct; 5, ductus sublingualis ma.ior; 6, palatine glands; 7, orbital or 

 zygomatic gland; cS', ducts of 7; .9, lacrimal gland. (Ducts colored red.) (After Ellenberger, in Leisering's Atlas.) 



crown of the first lower molar (Dens sectorius) is compressed laterally and has two 

 pointed, sharp-edged lobes, behind which are one or two tubercles; it has two roots. 

 The average periods of eruption are given below. 



TooTU ERri'TiON Changk 



I, 4 to .') weeks ] 



I2 4 to 5 weeks }• 4 to 5 months 



I3 4 weeks J 



C 3 to 4 weeks 4 to f) months 



P, 4 to 5 months ] 



P2 410/5 weeks . 



P3 3 to 4 weeks. 



P4 3 to 4 weeks . 



M, 4 months. 



f) to () months 



•»yr / upper .5 to 6 months 



M, 



'[ lower 4J2 to 5 months. 

 G to 7 months 



* Increase in number also occurs, the .sujx'rmunerary teeth being at either end of the series, 



