478 LEON AUGUSTUS HAUSMAN 
shaft of the typical shield hair rather than the shield. It may 
be that these hairs represent, anatomically, an expanded and flat- 
tened portion of the shaft element rather than an added shield 
element. The name shield hairs, however, in this case is not a 
misnomer when taken to refer to the form of the hair and not to 
its derivation. 
The cortex of the shield hair. The cortical element is that to 
which is primarily due the variations in form of the shield hair. 
In its simplest condition in the shaft of the hair it consists of 
elongated, distorted, fused, nucleated cells, which are compacted 
longitudinally as shown in figure 22. In the shield the cortex 
expands and comprises the major portion of that structure (figs. 
17 and 19). It is this element of the hair structure also which 
bears the pigment to which the color of the hair is due. In all 
but the cortex of the shield this pigment is distributed uniformly, 
but here it occurs most abundantly in the form of masses of 
granules in the ectal half of the shield (fig. 19). 
The relation of the cortex to the medulla and cuticle in the 
shield hairs of the feet and tail is shown in figures 25 to 29. 
The cuticular scales of the fur hair. The cuticular scales of 
the fur hair also differ in form from the base to the tip of the 
hair. Near the base the scales are very elongate (figs. 38 and 
39) and their free distal edges project away from the shaft, giv- 
ing to it a distinctly serrate profile (fig. 38). 
Near the middle of the hair the worn edges of the scales give 
the hair the appearance shown in figure 42, and near the tip that 
illustrated in figure 37. 
The medulla of the fur hair. No marked difference between 
the medulla of this type of hair and that of the shaft of the shield 
hair exists. Throughout four-fifths of the length of the shaft the 
medulla persists (fig. 42), and near the tip, where it does gradu- 
ally thin out and disappear, there is no place where it shows any 
modification in form such as that which is noted in the case of 
the shield of the shield hair of the dorsum. 
The cortex of the fur hair. This element presents no differences 
from its homologous structure in the shaft of the shield hair. 
