THE MAMMALIAN NEKVOUS SYSTEM 93 



for examination at the close of the course, with the laboratory 

 notebooks. So far as possible indicate the source of the 

 stimulus for each fiber system (sense organ, motor areas of 

 cerebral cortex, or associational nucleus, etc., as the case may 

 be), the complete course of the path, the number of neurons 

 involved in the path and their limits, collateral reflex connec- 

 tions, and the organ at which the path terminates. 



A useful exercise is to imagine a localized injury which de- 

 stroys a particular center or .tract or group of tracts at some 

 point, and then to determine what symptoms would result from 

 the injury in question. 



9. Optional Dissections of the Brain Stem 



102. The dissections described in the preceding pages can 

 be performed upon either sheep or human brains ,even though 

 the latter be not very well preserved. In the following pages 

 (Sections 103 to 111) directions are given for a more complete 

 dissection of some of the structures of the human brain stem 

 than it is practicable to carry out upon the sheep's brain, and 

 for these dissections well-preserved human brains which have 

 been hardened in formalin are necessary. All of these dis- 

 sections can be performed on one lateral half of the human 

 brain, save that the connections of the cerebellar peduncles 

 (Sections 103 to 105) within the cerebellum cannot easily be 

 demonstrated in case the cerebellum has previously been 

 removed as described in Section 49. 



These dissections, being in some cases more difficult than 

 those previously described, can best be done as a review exer- 

 cise after completion of the preceding exercises. Upon com- 

 pletion of the dissection of Sections 103 to 111 preserve the 

 specimen for later use (Sections 141 to 151). 



103. Corpus Restiforme. Upon lifting up the posterior bor- 

 der of the cerebellum a strong band of fibers is seen leaving the 

 posterior part of the cerebellar peduncle complex to turn back- 

 ward along the dorso-lateral border of the oblongata. This, 

 the corpus restiforme, is crossed immediately behind the cere- 

 bellum by the dorsal root and nucleus of the VIII nerve (tuber- 

 culum acusticum). Cut .through this cochlear VIII root and 

 reflect its fibers so as to expose the dorsal aspect of the corpus 



