SALIVARY GLANDS OF MAMMALS. 401 



and two inches thick posteriorly, and becoming thinner towards 

 the outer and anterior border, where the apex is prolonged 

 into a slender process. The isthmus, or base of the combined 

 glands, overlies the anterior half of the thorax ; the base of each 

 lateral lobe is notched by the prominence of the shoulder-joint, 

 round which its outer border extends ; the contracting anterior 



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prolongations of the gland pass forward along the sides of the 

 neck, external to the sterno-maxillaries, and terminate a little in 

 advance of the angle of the jaw. 



The tAvo packets of ducts, which indicate the essential double- 

 ness of the gland, emerge from the inner and posterior part of 

 the lateral lobes, five or six inches in a straight line from the 

 posterior border of the isthmus, and nine or ten inches from the 

 anterior attenuated extremity of the gland. After a short course, 

 the ducts dilate and form a small reservoir on each side ; they 

 are here so closely covered and connected by elastic cellular 

 tissue as to seem a single reservoir ; they maintain, however, 

 their distinctness, and continue, contracted, from each dilatation, 

 as three closely united attenuated ducts, which at length unite 

 into one long and slender duct. The dilated portion is sur- 

 rounded by a compressor muscle (constrictor salivaris). The 

 gland is conglomerate, the primary lobes being for the most 

 part oblong, subcompressed, from about three to nine lines in 

 diameter. The closely united ducts, after quitting the reser- 

 voir, are continued forward covered by the extraordinarily ex- 

 tended mylohyoideus, and, after their union, the common duct 

 terminates at the symphysis of the lower jaw. 



The parotid gland is small in proportion to the animal : it is 

 situated in front and below the root of the ear, is of a triangular 

 form, two inches four lines in length, one inch two lines in 

 breadth, with the duct continued from the outer side of the an- 

 terior apex of the gland, which apex terminates at the posterior 

 end of the origin o f the masseter muscle. The duct extends for- 



O 



ward along the outside of the masseter near its origin, passes 

 along the buccinator near its upper border and beneath the ten- 

 dons of three of the retractors of the mouth, then dips under the 

 orbicularis oris, and terminates near the opening of the mouth. 

 The length of the duct is eleven inches, its diameter scarcely 

 half a line. This is perhaps the longest duct, in proportion to 

 the size of the gland, in the animal kingdom : as the submaxillary 

 is the largest gland outside a visceral cavity in the vertebrate 

 series. The depressor auris, which arises from the angle of the 

 jaw, perforates the parotid gland. A chain of lymphatic glands 



VOL. III. D D 



