468 MANIPULATION. 



around the central part or shaft ; these are least numerous at 

 the base of the hair, as shown at fig. 2, but gradually increase 

 in number and size towards the apex, as seen in fig. 1, near 

 which they are very abundant, but do not project so far 

 beyond the shaft; this may readily be seen by contrasting 

 fig. 3 with fig. 1. In some hairs the succession of whorls 

 resembles very much a series of conical bags placed one within 

 the other; the principal parts of the hair that form a test of 

 the defining power of a half-inch object-glass, are the delicate 

 points that surround the upper edge of each whorl; these, 

 with a well-constructed combination, should be shown exceed- 

 ingly sharp, and the whorls themselves made to stand boldly 

 out from the shaft ; in some of the small species of English 

 bats, the whorls are arranged in a spiral form ; but in this 

 specimen there is plainly no such disposition. 



Mouse Hair. — The hair of this common little animal differs 

 materially both in structure and in size from that of the bat 

 above noticed ; at B, in plate vi., are shown four parts of a 

 large dark hair, whilst at D, in the same plate, corresponding 

 portions have been selected from a small flat hair. At B 1 is 

 shown the base of one of the large hairs, on which are certain 

 markings, whilst in 2 and 3 the internal structure is seen to 

 be cellular, there being three or more cells in each row, the 

 colour of the hair depending upon the greater or less amount 

 of the black pigment contained in the cells. When viewed 

 with a power of 100 or 200 diameters, all the light parts 

 should be shown distinctly from the dark, and the hne of sepa- 

 ration of the two correctly defined. The apex of the large 

 hair is seen at 4 ; it is of very small size as compared with the 

 central portion, and exhibits no trace of cell in its interior. 



At D are shown four parts of one of the small flat hairs 

 from the same animal ; the structure of the base and apex, as 

 seen at 1 and 4, is similar to that of the larger hair ; but the 

 internal structure of the intermediate portions, as exhibited at 

 2 and 3, is very different ; in 3, the dark cells extend entirely 

 across the hair, and are arranged at equal distances, whilst at 

 2 a rudimentary form of cell, containing a small quantity of 

 pigment, is seen to occupy the central portion of the shaft. 



