Chap. IV.] 



SALIVARY GLANDS. 



developed in the Lacertilia, and very richly so in the 



poisonous Heloderma of Mexico ; in correspondence 



with the position of these glands the 



reptile is said to turn on its back 



when striking its prey (Fischer) ; the 



secretion of these sub maxillary 



glands has certainly poisonous effects, 



}}ut the blood of a guinea-pig killed 



by it does, unlike the blood of the 



victim of the bite of a colubrine 



snake, but like that of the victim of 



a viperine snake, coagulate after 



death (Fayrer). In the venomous 



Ophidia the poison is supplied by 



the labial gland, which lies along the 



edge of the upper jaw, and has its 



duct opening into the maxillary 



tooth. 



The salivary glands are small in 

 river tortoises, and absent in the 

 marine Chelonia, and in the alligator, 

 where the glands are confined to the 

 tongue. 



In Birds, again, lingual glands 

 are well developed, but, as may be 

 supposed, the labial are altogether 

 absent ; in the wood-peckers, where 

 the tongue is protruded with great 

 rapidity (see page 156), the sub- 

 linguals are enormously developed, 

 and provide a sticky secretion, which 

 acts like bird-lime. 



In the Mammalia, three pairs of large, ordinarily 

 acinous, glands predominate over the smaller and 

 more scattered bticcal glands ; these, from their posi- 

 tions, are distinguished as the parotid, submaxil- 

 lary, and subliiiguals. From our knowledge 



seen from below, 

 showing the large 

 Sublingual Glands 

 (i, i), the Hyoid 

 Bones (e), and 

 the Base of the 

 Tongue (/). (After 

 Macgillivray.) 



