48 THE SHEEP AND WOOL INDUSTRY 



In the centre of almost every wool fibre there is a small 

 hollow tube which is known as the medulla. The medulla varies 

 a lot in diameter in the different classes of wool and hair. The 

 average diameter is from one-eighth to a quarter of the diameter 

 of the whole fibre. The medulla, as I have stated before, varies 

 a good deal and may just be visible in some cases, perhaps 

 disappearing altogether in portions of the fibre, more especially 

 in those fibres which are diseased. The medulla supplies all 

 the juices and nourishment to the fibre which are necessary for 

 its growth. It also contains the pigment matter which gives to 

 the wool its various colours grey, black, etc. The medulla of 

 the wool fibre plays a very important part in the dyeing processes 

 which wools have to undergo. The colouring or dyeing matter, 

 obtaining access to the medulla at the cut end of the fibre, will 

 run up the small tube and thus thoroughly dye the centre of the 

 fibre, and owing to the fibre's porous and transparent nature, 

 the dye will go through the whole of the fibre, and give it a 

 beautiful, even colour. In some wools the outside layer of scales 

 will not take the dye too readily, and in some cases, such as 

 kempy fibres, it will not take the dye at all, because they are not 

 porous, though the dye will sometimes gain access to fibre at the 

 interstices of the scales. This is one of the reasons why kempy 

 wool is so objectionable to manufacturers. The kempy fibres 

 have long, non-porous closely fitting scales, that will not take the 

 dye, the consequence being that the material containing them will 

 have white, hairy fibres through it, giving it a speckled appearance. 

 A fibre may have non-porous and closely fitting scales that 

 will not take the dye, but its medulla may be large and even, 

 and the dye will go up to the end of the fibre and will show 

 through the transparent sides, just the same as a white glass 

 bottle filled with a coloured solution would appear. Pulled, or 

 slipe wool that is, wool which has been taken off a sheep- 

 skin is much harder to dye than shorn wool, as the flesh end 

 of the fibre is generally closed owing to the juices of the hair- 

 follicle hardening. On examining the flesh end of pulled wool 

 you will also notice a small skin-like material covering the 



