HYPOGLOSSAL GANGLIA OF PIG EMBRYOS 



267 



the ganglionic chain running forward to the vagus. This commis- 

 sure could not be subdivided into definite ganglia ; it was charac- 

 terized by irregular swellings and spurs." 



Streeter ('04) in tracing the development of the peripheral 

 nerves in human embryos finds a ganglionic crest extending from 

 the first cervical to the superior ganglion of the glossopharyngeal 

 and partly ensheathing the fibers of the spinal accessory nerve. 

 In embryos 10 to 13 mm. long the neural crest becomes differenti- 

 ated into four or five rather diffuse cell masses. Froriep's ganglion 

 resembles the others, being irregular in form and without roots. 

 The hypoglossal nerve originates as four or five parallel roots. 

 There is no correspondence between these and the rudimentary 

 ganglia, nor are the ganglia segmentally arranged. He considers 

 the three or four anterior cell masses as cerebral ganglia and 

 "not to be confused with the precervical ganglion of Froriep." 



MATERIALS AND METHODS 



The number and length of the embryos dissected are given in 

 the following table: 



All drawings were made with the aid of an Abbe camera lucida 

 and a Zeiss a* objective. The embryos were fixed in Zenker's 

 fluid and the dissections were first stained, cleared in creosote and 

 drawn as transparent objects. It was thus possible to locate micro- 

 scopic cell masses and trace the course of very small fiber bundles. 

 The dissection was then transferred to alcohol and examined as 



