34 LABORATORY OUTLINES FOR EMBRYOLOGY 



b. Transverse Sections 



The transverse sections should be parallel to the length 

 of the hind-brain. Indicate on your drawing of the whole 

 embryo the region from which each section is taken. 



(i) Through the Anterior Part of the Otocyst 



This section passes through the body twice. The 

 hind-brain has a very thin dorsal wall. Its lateral walls 

 have several irregular folds, the neuromeres. The fore- 

 brain appears as an oval section of the central nervous 

 system. On either side of the body near the hind-brain 

 are the otocysts. The rather sharp evagination of the 

 otocyst extending toward the hind-brain is the endolym- 

 phatic duct. Ventral to the otocyst and between it and 

 the hind-brain is the acustico-facialis ganglion. To the 

 side of the hind-brain and almost between it and the 

 fore-brain is the large trigeminal ganglion. Dorsal to 

 the otocyst and to the side of the hind-brain is the vagus 

 ganglion. Dorsal to the vagus ganglion may be seen 

 fibers of the spinal accessory nerve. 



Draw the section, color the germ-layers, and label all the 

 parts. 



(2) Through the Choroid Fissure and the Optic Stalk 



This section passes through the fore-brain and the 

 spinal cord. The spinal cord has differentiated into 

 two distinct zones, the dorsal zone and the ventral zone. 

 From either side of the spinal cord may be seen the roots 

 of the spinal nerves. The notochord is small compared 

 with the notochord of the chicken. Identify the jugular 



