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PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



or where it is inserted into the jaw, and its posterior extremity seized with a pair 

 of artery forceps and gradually cleared back to its insertion in the temporal bone 

 and surrounded by a ligature. When it is assured there is nothing but muscular 

 structure in the grasp of the ligature, it is pushed back to the temporal bone and 

 tied, and the digastric muscle divided in front of the ligature and removed. On 

 carefully tearing away the connective tissue at the base of the wound and drawing 

 back the submaxillary gland, there is exposed a triangular cavity (Fig. 121). 

 This space is limited above and behind by the under surface of the submaxil- 

 lary gland, into the hylum of which enter the artery, chorda tympani and sym- 

 pathetic nerve fibres, and the glandular duct. Its lower margin is formed by 

 the genio-hyoid muscle, and its upper border by the ramus of the jaw and the 

 masseter muscle. The anterior portion of its floor is formed by the transverse 

 fibres of the mylo-hyoid muscle, on which ramify the branches of the mylo-hyoid 

 nerve. At the posterior portion of this space the external carotid artery enters 

 and runs along the base of the triangle, giving off first the lingual and then the 



FIG. 121. PARTS EXPOSED IN OPERATIONS ON THE SUBMAXLLLARY GLAND 

 OF THE DOG. (Bernard. 



M, anterior portion of digastric muscle elevated with a tenaculum ; M', posterior extremity of the 

 digastric raised up so as to show the carotid artery, 1 1, and the sympathetic filaments ; G, sul.maxillary 

 gland elevated to show its posterior surface: H, submaxillary and snblingual ducts: J. external jugular 



. 



vein; J', posterior branch; J", anterior branch: D, glandular vein; F, origin of inferior glandular 

 artery; P, hypoglossal nerve; L, lingual nerve: T, chorda tympani; S S', divided mylo-hyoid muscle; 

 U, masseter muscle at angle of lower jaw ; Z, origin of mylo-hyoid nerve. 



facial arteries, from off the latter of which comes the artery of the gland. Almost 

 immediately after entering this space the carotid is crossed by the large hypo- 

 glossal nerve, running forward to be distributed to the muscles of the tongue. If 

 this nerve is divided at the point where it crosses the carotid, and the central end 

 removed, the pneumogastric nerve comes into view, lying behind the artery. On 

 pulling to one side the vagus trunk, below and behind it can be seen the white 

 trunk of the sympathetic nerve, which here separates itself from the vagus to 

 form the superior cervical ganglion, from which two small filaments pass out to 

 accompany the carotid and the artery of the gland to enter the hylum. Some of 

 the sympathetic fibres also pass into the gland along the arterial branch which 

 comes from the temporal branch, and enter the exterior part of the gland. Then, 

 to expose the chorda tympani and salivary ducts, the fibres of the mylo-hyoid 

 muscle are to be divided transversely at about their middle, avoiding every nerve, 

 but tying all veins, and the upper half of the muscle reflected. The lingual nerve 

 then comes into view, passing from under the ramus of the jaw and running 



