3o8 



THE NATURE BOOK 



tinge of delicate purple which can, under case with Moles and Shrew Mice, the 

 certain conditions of top lighting, be wave of the hair is combined with extreme 

 seen on the shadowed portions of an fineness, a colour-effect produced by light- 

 orange plum, can be fairly matched by interference may reasonably be expected, 

 the appearance of a Pygmy Shrew's While making the above measurements 



fur under a similar illumination. 



The explanation of this irides- 

 cence, or bloom, as I prefer to call 

 it, is to be found in the structure 

 of the individual hairs, and this 

 structure also accounts for the 

 velvet quality of the fur as a whole. 

 It has been very frequently stated 

 that the hairs of the Mole are 

 rooted perpendicularly in the skin 

 instead of sloping with a definite 

 " set " from front to back. I have 

 not been able to find any justifica- 

 tion for this statement, and I 

 think that the absence of any 

 definite "set" in the fur of this 

 class of animal is to be more 

 naturally explained by the fact 

 that each individual hair is com- 

 posed of live thicker, and four 

 narrower portions in alternate 

 order. Taking the hair of the 

 Common Shrew Mouse, and start- 

 ing at the root end, we find that 

 transverse measurements at the 

 centres of the alternate wide and 

 narrow portion work out as fol- 

 lows : -ooS millimetres, -006 milli- 

 metres, -012 millimetres, -006 

 millimetres, -016 millimetres, -006 

 millimetres, -020 millimetres, -006 

 milhmetres, -024 millimetres. From 

 the last point of measurement the 

 hair tapers to the tip. At each of 

 the four narrow portions, where 

 the remarkable fineness of -006 

 millimetres occurs, the hair makes 



■OOS 



•006 



•0/6 



•006 



ifOOT 

 SKETCH 



(and I would here take the oppor- 

 tunity of expressing my indebted- 

 ness to my friend Mr. O. H. Latter 

 for his assistance in the matter) it 

 occurred to me that the alternation 

 of thicker and thinner portions in 

 each hair, as viewed under the 

 microscope, might arise from the 

 hair being more or less ribbon- 

 shaped and twisted spirally, so 

 that one saw alternately the width 

 and the edge of it. 



The possibility of this was sug- 

 gested by the fact that from the 

 root end to about the middle of 

 the hair there appeared to be 

 short lengths of serrations on alter- 

 nate sides. 



Successi\'e cross sections have 

 shown me, howe\'er. that the hair 

 is cylindrical for the greater part 

 of its length, and that it is only 

 where the spear tip is reached that 

 it tends to become elUptical in 

 cross-section, owing to a slight flat- 

 tening of the cells which compose 

 this portion of it. 



While we are on the subject of 

 hair, mention should be made of 

 the side glands in the male Shrew 

 Mouse, which can best be detected 

 by the feel of the coarser hair 

 immediately surrounchng them. 

 They are especially developed in 

 the spring, and as may be seen 

 from the illustration on page 309, 

 are situated on the animal's sides 

 at points rather forward of the 



an abrupt bend, and these bends 



are in alternate directions. Each diagram of middle of his body. They consist of 



standing hair, therefore, yields to "sIIkew^ ''^^^'^ ^^"^ patches (orange-coloured 



the touch in four different places mouse. on their under surfaces) in the 



at once, a fact which accounts centres of which are small, thick 



not only for the velvet softness of the j^rotuberances surrounded by stiff, coarse 



fur as a whole, but also for the ab- hairs. Sections through these patches 



sence of a set in any definite direction. 

 So far as the bloom is concerned, I think 

 we may find a certain analogy in the 

 wavy hair, of which certain human 

 beings are the fortunate possessors. Wavy 



show that they are true glands, con- 

 taining ducts, and the secretion from 

 them probably helps to create the dis- 

 agreeal)le musky odour which is pecu- 

 liar to the animal, and which is most 



hair tends to scatter and reflect light in searching when the animal is annoyed. 

 opposed directions, and when, as is the That they are not wholly responsible is 



