8 Howard Avers and Julia Worthington 



give out very thick protoplasmic processes. Sometimes the axone is 

 found to arise from one of these processes at a little distance from the 

 body of the cell; in other cases, however, it is impossible to distinguish 

 the axone from the other processes. 



The connections established by these large cells are quite various. 

 Some of them send their axones ventrad into the ventral motor column 

 of the same side of the brain; some send them across the brain through 

 the ventral raphe. Sometimes they apparently serve to establish con- 

 nection between different parts of the nucleus. The cell in Fig. 31 

 lies about in the center of the nucleus and sends one process dorsad and 

 the other ventrad, where it divides in the extreme ventral part. It is 

 possible that the cell processes, though not to be followed in this section, 

 really penetrate beyond the acusticum into the general cutaneous 

 nucleus. In some horizontal sections large cells lying in the dorsal part 

 of the nucleus near the middle send axones caudad into the dorso- 

 caudal part. In one section a fiber was seen that, though it could not 

 be traced to a cell, resembled in every particular the axones of the large 

 cells in the same locality; this fiber, first seen in the dorsal part of the 

 acusticum of the left side of the brain, slightly cephalad of the middle, 

 crossed to the dorso-caudal part of the nucleus of the right side. 



Many of these cells lie on or near the borders of the nucleus and 

 send their processes into adjacent parts of the brain. In Fig. 37 the 

 cell lies on the ventral border of the acusticus nucleus; processes 1, 2 

 and 3 go into the upper layers of the acusticum, while process 4 divides 

 into branches that penetrate into the general cutaneous nucleus. Fig. 

 38 shows a cell lying in the lateral part of the nucleus that sends 

 process a into the nucleus, and processes d^ and d' into the general 

 cutaneous nucleus. In this cell a appears to be the axone. Fig. 43 is 

 a similar cell in the cephalic end of the acusticus nucleus which sends 

 its axone into the nucleus, processes rf^ an'd d- into the general cutaneous 

 nucleus, and d^ among the fibers of the fasciculus communis. On the 

 other hand, cells are sometimes found that lie in the general cutaneous 

 nucleus close to the acusticum that send some of their processes into the 

 acusticum while their axones remain in the general cutaneous nucleus 

 (Fig. 40). Thus the connection is established in both directions between 

 these two important centers of the medulla. 



The Secondary Fiber Tracts of the Acusticum. — Thus far we have 

 considered the connection of the acusticus nucleus with other parts of 

 the brain by means of individual cells located in various parts of the 



