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 upper 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 backwartl. 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. e., 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 



^^ 



Firi. 329. — Dissection of Head of Dog, Showing Salivary Glands, etc. 

 o. Ocular muscles; b, pterygoideus internus (cut); c, stylo-glossus; d. digastiicus (cut); e, genio-glossus; 

 /, genio-hyoideus; </, hyo-glossus; h, thyro-pharyngeus; i, crico-pharyngeus; k, thyro-hyoideus; I, zygomatic 

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

 S', anterior part of same; 4, submaxillary duct; 5, ductus sublingualis major; 6, palatine glands; 7, orbital or 

 zygomatic gland; 8, ilucts of 7; 9, lacrimal gland. (Ducts colored red.) (.\fter Ellenberger, in Leisering's .\tlas.) 



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. 



Tooth Eruption Change 



Ii 4 to 5 weeks ] 



I2 4 to 5 weeks !■ 4 to .'i months 



I3 4 weeks J 



C 3 to 4 weeks 4 to 5 nionth.s 



Pi 4 to 5 months ] 



P2 4 to 5 weeks 



P3 3 to 4 weeks 



P4 3 to 4 weeks 



Ml 4 months 



lyr / upper .5 to 6 months. 



5 to () months 



M, 



\ lower 43^ to 5 months. 

 . () to 7 months 



Increase in number also occurs, the sui)cnuimerary teeth being at either en<l of tlie series 



