432 



SALIVARY GLANDS. 



A. Salivary vessels opening into the mouth, 

 generally beneath the tongue, and more 

 seldom at the base of the mandibles. 

 They take the following forms : 



1 . Simple, long, undivided, twisted tubes : 

 thus in the majority of insects, viz. all 

 butterflies, many beetles and flies. 



2. As a narrow vessel which empties it- 

 self into one or two bladders, whence 

 the salivary duct originates (Nepa, 

 Cimex, Sarcophaga). 



3. As a ramose vessel with blind branches 

 (Blaps). 



4. As two long cylindrical pipes, which 

 unite into one excretory duct. 



5. As four small round bladders, each 

 pair of which has a common duct 

 (Pulex, Lygoeus, Cimex). 



6. As a multitude of such vesicles in 

 Nepa. 



7. As capitate tubes, in the free ends of 

 which many very fine vessels empty 

 themselves (Tabanus). 



8. As tubes which at intervals are sur- 

 rounded by twirling blind bags (Ci- 

 cada) . 



9. As granulated glands which on each 

 side unite into a salivary duct, both of 

 which join into a single evacuating 

 duct (Gryllus). 



B. Salivary glands which empty them- 

 selves into the commencement of the 

 stomach, as short or long bags, either 

 simple or furnished with processes (Bu- 

 prestis); other forms as well as those just 

 cited, are found among the Diptera : 



1. As two capitate tubes, into the free 

 ends of which many delicate vessels 

 open (Hemerobius perla). 



2. As two short processes of the same 

 width as the stomach (Leptis and 

 Acheta). 



3. As two bags covered entirely with 

 short blind processes (Bombylius, Bu- 

 prestis). 



4. As triangular processes, each edge of 

 which is occupied by a row of vesicles 

 (Chrysotoxum). 



5. As six narrow tubes which surround 

 the commencement of the stomach 

 (Gryllus). 



6. The blind processes which clothe the 

 stomach in the predaceous beetles. 



In Cirrhopoda the salivary glands are two 

 in number and of considerable size, opening 

 into the commencement of a short oesopha- 

 gus. 



Among Pteropoda they are found in Clio 

 as two long and slender glands placed at the 

 sides of the oesophagus, and pouring their 

 secretion into the mouth. They " present in 

 the Gasteropoda different forms and degrees 

 of development bearing the ordinary relations 

 to the construction of the mouth and the 

 nature of the food. In the Calyptraa they 

 are represented by two simple elongated se- 

 creting tubes. In the whelk they present a 



conglomerate structure, and are situate at 

 each side of the oesophagus at the base of the 

 proboscis, along which they transmit their 

 slender ducts to terminate on each side the 

 anterior spines of the tongue." (Owen.) In 

 the snail they are flattened, elongated, and 

 irregular in form, and conglomerate in struc- 

 ture, diminishing in breadth as they proceed 

 upwards to the pharynx, where their ducts 

 terminate. In the Vaginulus an additional 

 slender tube which lies first on the stomach, 

 passes through the nervous collar to join the 

 duct by which the saliva is discharged. 



The salivary glands are present in all the 

 Cephalopoda, with the exception of Loligo- 

 psis. In the Onychoteuthis two glands are 

 situated at the root of the tongue. "" They are 

 in general, however, four in number, two at 

 the root of the tongue, which give off distinct 

 ducts which terminate at the commencement 

 of the oesophagus ; the other pair, generally 

 longer than the superior, is lodged in the vis- 

 ceral sac, on each side of the upper part of 

 the crop. The ducts of the last form a single 

 tube which opens in the neighbourhood of the 

 spiny portion of the tongue. 



The salivary glands are absent in Pisces. 



Among reptiles in the C/ielonian, Saurian, 

 and Batrachian orders, the substance of the 

 tongue seems principally made up of a glan- 

 dular mass formed by a multitude of little 

 tubes united at their bases, but becoming se- 

 parate towards the surface of the tongue. In 

 the Ophidian reptiles two glandular organs 

 placed immediately beneath the skin of the 

 gums surround the margins of the upper and 

 lower jaw, and pour an abundant salivary 

 secretion into the mouth. (Rymer Jones.) 

 In many genera the salivary apparatus is de- 

 ficient. The poison glands of serpents can 

 hardly be reckoned among the salivary organs, 

 being destined for a special secretion, and 

 forming the analogues to similar glands' in the 

 Arachnida. 



In Aves the salivary glands present con- 

 siderable variation in their number, position, 

 and degree of development. In the crow the 

 only indication of a salivary apparatus is a 

 series of simple cone-shaped follicles, placed 

 along the sides of the oral cavity, upon the 

 mucous membrane of which they open by 

 distinct orifices. In general, however, there 

 are four pairs, two sublingual on each side 

 beneath the tongue, two maxillary divided each 

 into an anterior and posterior, and opening by 

 special ducts in front of the tongue, and a gland 

 which can be compared to the parotid. These 

 are generally all present in the Rapaces, Pas- 

 seres, and GaUince ; and appear to be absent 

 in Sula, Carbo, and Phasnicopterus, and but 

 slightly developed in the Grallce and Palmi- 

 pedes generally. In the goose they occupy 

 the entire space included between the rami 

 of the lower jaw, being closely united in the 

 median line, and opening into the mouth on 

 each side of this by a series of orifices. 

 In the watercoot and Hirundo esculenta, 

 the parotid is highly developed, in the latter 

 the secretion serving for the preparation of 



