174 WILLIAM F. ALLEN 



to the gasserian ganglion, degenerated fibers were found in the 

 former, but not in the latter. 



According to these authors, the animals in which the mesen- 

 cephalic root had been severed showed no loss of power of the 

 masticator muscles or any functional loss of any kind. 



From these experiments May and Horsley concluded that the 

 mesencephalic root contamed both centrifugal and centripetal 

 fibers. The latter are sensory arising mainly from the gasserian 

 ganglion, while the former take origin from the globular cells of 

 the mesencephalon, but the authors do not exphcitly state 

 whether motor or sensory. They found, however, from Marchi 

 preparations, after a lesion had been made in the inferior collic- 

 ulus, that degenerated mesencephalic root fibers could be traced 

 through the motor root to end apparently in the gasserian 

 ganglion. 



In 1911 Willems published a most comprehensive monograph 

 on the mesencephalic root and masticator nucleus of the rabbit. 

 His investigations were based on anatomical-histological and 

 experimental methods. In the former he noted the difference 

 between the globular unipolar cells of the mesencephalic root 

 nucleus and the multipolar motor cells of the masticator nucleus 

 in a 22 mm. and adult brains; while in the latter he counted the 

 number of chromatolytic cells in the mesencephalic root nucleus 

 after one of the motor branches of the trigeminal nerve and in 

 one experiment the ophthalmic and maxillary nerves were cut. 

 The experimented animals were killed ten to eighteen days after 

 operation and sections of these brains were stained with tolui- 

 dine blue or neutral red. In addition to giving complete 

 descriptions of his experiments, the writer has summarized his 

 results in tabular form. He found a disintegration of many 

 ,cells in the 'mesencephalic root nucleus as the result of severing 

 the masseter, sphenoidal, or temporal nerves, and a lesser num- 

 ber after cutting the external or internal pterygoid nerves, while 

 no degenerated cells or scarcely any appeared after a lesion of 

 the digastric or mylohyoid nerves. The writer cites a number 

 of reasons for establishing the mesencephalic root as a sensory 

 nerve for the masticator muscles. It will be seen that Willems' 



