HISTOLOGY OF SENSORY GANGLIA OF BIRDS 271 



the chick being fixed in absolute alcohol, shrinkage might be 

 expected, but the ganglia of the goose were fixed in formalin which 

 tends to increase rather than diminish the size of the cells. The 

 capsular nuclei are quite numerous and lie not only in the peri- 

 cellular capsule but also along the process (fig. 38). Somewhat 

 similar nuclei are quite abundant in the intercellular space. 

 Those in the capsule are usually elliptical with a major axis 

 about twice the length of the minor, while those in the intercellular 

 space are much broader, being round to elliptical. They contain 

 one to two nucleoli. Figure 38 represents a typical cell of this 

 ganghon showing the nucleus centrally located with its central 

 nucleolus. The delicate sheath, cap., with its elongated nuclei, 

 c, are shown, also the nuclei, nu, of the intercellular space. 



D. SENSORY GANGLIA OF THE DUCK 



1 . Spinal ganglia 



The brachial ganglia of the mallard duck are much larger than 

 any other spinal ganglia of the same bird. This condition is 

 probably coordinated with their power of flight. As in the owl, 

 the ganglion cells can be divided into two classes on the basis of 

 their size. The large cells are fairly uniform in dimension; one 

 of the larger ones measured 44 fx long and 41 broad, with a nucleus 

 that had diameters of 14 and 12 ^ respectively. The smaller 

 cells, which are more numerous, average about 25 fj. in length and 

 20 in breadth. One of the smallest of this class measured 11 by 

 18 ju and had a nucleus 4 by 6 //. Outside of the brachial region 

 the spinal ganglia of the mallard are much smaller and there is 

 no division of the cells into two classes based on size. It is 

 true that there are a few quite large cells and very many small 

 ones, but there are numerous gradations between the extreme 

 sizes. 



One of the largest cells measured 71 ^ in length, and 39 in 

 breadth, with a nucleus 14 by 15 fj.. One of the smallest was 14 fx 

 in breadth and 15 in length, with a nucleus 4 by 5 /i. 



In the brachial ganglia as well as in the other spinals most of 

 the cells were rounded in shape, the remainder being elliptical 



