476 THE SALIVAR Y GLANDS. 



past them. Thus the gland has no proper hilus. The duct runs parallel 

 to and a little laterally of Wharton's duct. 



The main blood supply, both to the submaxillary and the sublingual 

 gland, is derived from a branch given off by the external maxillary 

 artery. The submaxillary division of this branch runs to the hilus of 

 the gland, and there divides. The submaxillary gland receives also one 

 or two small branches from the great (or posterior) auricular artery, 

 where this curls round the digastric muscle. 



The veins of the submaxillary gland are variable in position, and 

 somewhat variable in number. There are generally two ; they run a 

 short course, about half a centimetre, and then one enters the internal, 

 and the other the external, maxillary vein, a little before these unite to 

 form the external jugular vein. 



In the dog and cat there is a fairly large gland situated in the orbit, 

 and hence called the orbital gland. Its duct opens near the second 

 upper molar tooth. The orbital gland corresponds to the large buccal 

 gland, which in some animals is called the superior molar. 



In the rabbit, the only point we need mention is that the parotid 

 gland consists of two larger and thicker portions, a medial and a lateral, 

 connected by a thin central portion. By appropriate arrangement, the 

 thin central portion can be observed under a microscope, and the appear- 

 ance of the gland cells in life, and the variations of the blood flow in 

 varying conditions, can be observed. 



Occasionally in the dog, and more constantly in some other animals, 

 for instance the guinea-pig, a small gland, called by Klein l the inferior 

 admaxillary, pours its secretion into the duct of the parotid. It 

 may be regarded as a separated lobule of the parotid gland, although 

 its secretory cells are mucous, instead of being albuminous, thus 

 differing from the parotid secretory cells in general (cf. below, p. 478). 



In a considerable number of animals, a small mucous gland is 

 attached to the outer anterior end of the submaxillary gland. This 

 was described by Klein in the guinea-pig, and called by him the superior 

 admaxillary. The duct of this gland, according to Eanvier, runs parallel 

 to and on the outer side of Wharton's duct, but does not join it. He 

 calls it the retrolingual gland. 



Ranvier 2 considers that the customary use of the term sublingual gland is 

 in many cases erroneous. The sublingual, lie defines as a gland which has a 

 number of separate ducts the ducts of Rivini. But, besides the sublingual, 

 another gland occurs, which he calls the retrolingual gland. This is charac- 

 terised by having a single duct the duct of Bartholin running parallel to 

 Wharton's duct. An animal may have both sublingual and retrolingual, as 

 the guinea-pig, rat, and hedgehog ; or the retrolingual may be absent, as in 

 man, horse, sheep, and rabbit ; or, again, the sublingual may be absent, as in 

 the dog and cat. Thus Ranvier considers the gland usually called the sub- 

 lingual in the dog and cat to be the retrolingual. 



In different classes of mammals, the relative development of the 

 salivary glands varies. Thus in the horse the parotid is four to five times 

 the weight of the submaxillary gland, in the sheep and ox the weights 

 are not very different, in the dog the submaxillary gland is slightly 

 heavier than the parotid. 



1 Quart. Journ. Micr. Sc., London, 1881, p. 114. 



2 " Etude anatomique des glands," Arch, de physiol. norm, etpath., Paris, 1886. 



