HISTOLOGY OF SENSORY GANGLIA OF BIRDS 263 



Cells with the fenestrations, slings, and loops, while quite com- 

 mon in the old hen, are comparatively rare in young birds. Figure 

 24 represents a bipolar cell from a young bird showing a similar 

 though less complicated condition. 



The question of the presence of multipolar cells and of their 

 nature is an important one from the standpoint of the literature. 

 Accordingly, a careful search was made for such cells in the sen- 

 sory ganglia of the chick. The Gasserian, glossopharyngeal, 

 vagus, the cervical, dorsal and lumbar spinals were analyzed 

 without finding any cell that should be properly classified as 

 multipolar. There is a clearly defined difference between multi- 

 polar cells as observed in the sympathetic ganglia of the chick, 

 and the cells with accessory processes of the sensory ganglia. 

 A comparison of figures 18 and 19 will illustrate this difference. 

 In figure 19 the accessory processes are very fine as compared 

 with the neuraxon, they are entirely included within the capsules, 

 and, in the majority of instances, each ends in a bulb. In figure 

 18, which is a sympathetic ganglion cell, the processes that pass 

 beyond the capsule are large and of fairly uniform size. In the 

 intercellular space they divide into numerous branches. More- 

 over this cell (fig. 18) has slings and accessory processes, confined 

 within the capsule, that are similar to those of sensory cells. It 

 appears, therefore, that the supernumary processes that make the 

 sympathetic a 'multipolar' cell are not present in sensory cells, 

 while the sympathetic type of cell has accessory processes similar 

 to those found on the cells of sensory ganglia and in addition, has 

 its supernumary processes extending beyond the capsule. 



The principal sympathetic ganglion in close proximity to a 

 cerebral ganglion lies just beneath the vagus. It can, however, 

 be readily separated from that ganglion. In the cervical region, 

 also, the spinal and sympathetic ganglia are separate, but the 

 dorsal spinals are closely united with the sympathetic. Sections 

 of the dorsal spinal ganglia show cells of sympathetic type close 

 to those of sensory type. The space between sympathetic cells 

 and those of truly sensory type is often less than the diameter 

 of an average sensory cell, and their capsules appear in some 

 instances to touch. Thus it is easy to account for the multipolar 



