GOO ORGANS OF SECRETION. 



part of the broad short neck, and appear to serve as a means 

 of defense. No unequivocal thyraus gland appears to be 

 developed in the amphibia or in the fishes, and it is only a 

 deciduous organ of the foetus in higher vertebrata. 



The impervious scaly covering of terrestrial air-breathing 

 reptiles, is less compatible with the high development of 

 cutaneous muciparous glands, than the soft and often naked 

 skins of aquatic vertebrata, and this external deficiency is 

 compensated for by the increased secretions of internal glands; 

 nearly similar conditions exist in most birds and mammalia. 

 The sublingual salivary glands are always distinct in serpents, 

 and also the superior and inferior labial glands, and the parotids 

 or foliated temporal glands in the noxious species, transmit 

 their poisonous secretions through the perforated fangs. The 

 poison gland of serpents occupies the situation of the paro- 

 tid, below and behind the eye, on each side of the head, 

 and consists of numerous symmetrical compressed Iobes 3 

 each composed of minute diverging branched follicles, and 

 the common duct of all the lobes passes forward along the 

 side of the upper jaw to the base of the perforated fang, 

 where it enlarges to form a wide reservoir for the secretion, 

 and is surrounded with muscular fibres to compress it when 

 required, and force the poison into the tooth. The upper 

 and lower labial or maxillary glands consist of vertical, 

 parallel, simple, contiguous lobes opening into the mouth by 

 separate orifices. The salivary and muciparous glands are 

 also distinct in the saurian, and especially in the chelonian 

 reptiles where the submaxillaries are most developed. 



The liver of reptiles is large, little divided externally into 

 lobes, composed of minutely pinnated follicles or acini, pro- 

 vided with a gall-bladder, and an extensive portal circulation, 

 and there are commonly hepatic ducts passing directly from 

 the liver to the duodenum, besides the duct from the gall- 

 bladder. This organ varies its external form with the general 

 form of the animals, being remarkably elongated in the 

 ophidian, broad in the chelonian, and intermediate in the 

 saurian reptiles. The hepatic ducts of the ophidia alternate 

 with the separate ducts of the pancreatic lobes, in their 

 points of entrance into the duodenum, near the pyloric 

 valve. The pancreas presents a more concentrated form in 

 sauria and chelonia than in ophidia, and the spleen is also 

 relatively small in serpents where it is closely united to the 



