338 EMBRYOLOGY. 



bronchial tubes, and a broader vesicular terminal part. 

 In the second stage the air-cells or pulmonary alveoli 

 are formed. 



14. From the intestinal canal proper there are formed only two 

 glands, which are large and developed from the duodenum the 

 liver and the pancreas. 



15. The liver is developed as a branched tubular gland which 

 becomes a network. 



(a) There grow out from the duodenum into the ventral 



mesentery or prehepaticus (Vorleber) two liver-tubes, 

 the fundaments of the left and right lobes of the liver. 



(b) The tubes form hollow or solid lateral branches, the 



hepatic cylinders, which are united into a network and 

 become in part bile-ducts, in part the secretory paren- 

 chyma of the liver and biliary capillaries. 



(c) The ductus choledochus arises as an evagination of the 



wall of the duodenum which receives the two hepatic 

 tubes, and it forms at one place an evagination which 

 becomes the gall-bladder arid the cystic duct. . 



16. From the ventral mesentery, into which the hepatic tubes 

 grow, are derived the serous investment and a part of the ligamentous 

 apparatus of the liver, namely, the lesser omentum (ligamentum 

 hepato-gastricum and hepato-duodenale) and the ligamentum sus- 

 pensorium hepatis. 



17. The pancreas grows from the duodenum into the dorsal 

 mesentery and into the mesogastrium. 



18. The mesentery which the pancreas originally possesses subse- 

 quently disappears by becoming fused with the posterior wall of the 

 trunk ; at the same time, in consequence of the twisting of the 

 stomach, the long axis of the pancreatic gland comes to lie in 

 the transverse axis of the body. 



LITERATURE. 



Afanassiew. Weitere Untersuchungen iiber den Bau und die Entwickelung 



der Thymus und der "VVinterschlaf druse der Saugethiere. Archiv f. mikr. 



Anat. Bd. XIV. 1877. 

 TJemmelen, van. Die Visceraltaschen und Aortenbogen bei Eeptilien und 



Vogeln. Zool. Anzeiger, Nr. 231, 232, 1886, pp. 528, 543. 

 Bemmelen, van. Ueber die Suprapericardialkb'rper. Anat. Anzeiger, Jahrg. 



IV. 1889, Nr. 13. 

 Bemmelen, van. Die Halsgegend der Reptilien. Zool. Anzeiger, Jahrg. X. 



Nr. 244, 1887, p. 88. 



