82 D. A. RHINEHART 



gives pieces of the nerve for study. To a certain extent, this 

 difficulty probably accounts for some of the conflicting state- 

 ments as to the distribution and function of the nerve in these 

 forms. In lower vertebrates, in which it has usually been fol- 

 lowed in its entire course in serial sections through the heads of 

 small animals, the study of the nervus facialis has given far 

 more uniform results. 



After a futile attempt to obtain satisfactory material from man 

 and certain of the larger mammals for an investigation of the 

 mammalian facial nerve, it occurred to me that a better proced- 

 ure would be to follow the method used so successfully on lower 

 vertebrates and select for use a small mammal, the head of 

 which could be cut in serial sections. Because of the abundance 

 of the material and because the size of the head readily permitted 

 of the preparation of serial sections, the albino mouse was chosen 

 for this work. 



MATERIALS AND METHODS 



The material used consisted of a number of series of sections 

 of whole and half heads of 14-, 21-, and 23-day-old albino mice, 

 mice of this age being selected because of the small size of the 

 head and because the bones could be easily decalcified. The 

 series were prepared by the pyridine silver technique following 

 decalcification as originally used by Huber and Guild ('13 a). 

 The original method was varied in that the vessels w^ere first 

 washed out with normal salt solution, and the stained material 

 was imbedded in both celloidin and paraffin. The double im- 

 bedding was found necessary because of the small pieces of hair 

 which were scattered over the sections when the blocks are im- 

 bedded in paraffin alone. 



This modification of the pyridine silver method gives excel- 

 lent results. The main trunks and branches of the nerves, 

 nerve fibers in muscle and connective tissue, the ganglion cells 

 on the roots of the cranial nerves and the cells and fibers in the 

 central nervous system are well impregnated. The nerves in 

 the glands and the cells in the sympathetic ganglia are the poorest 

 stained of any parts of the cranial nervous system. In the sym- 



