If we examine many samples of wool we shall not be long before we encounter certain specimens showing one or more constrictions. Now we all know that the reason why some people do not grow very much is because they are delicate, ill health affects the whole system. The constrictions in the sheep’s wool occur because the animal has suffered from some illness, or from great hunger or thirst, which has resulted in its wool not growing properly for a period corresponding to the duration of the illness or other calamity. The examination of various animal hairs will help to while away many an hour and many of these objects are of the greatest interest. If we have the opportunity it will be interesting to compare the wool from different kinds of sheep, that from the Lincoln sheep, for example differs from that of shortwooled kinds. We may also compare goat’s wool with sheep’s, then there are differences between the hair of cows and calves. Comparisons always make microscopic work more interesting. The microscopic examination of cloth, used for making our coats, is quite interesting work and withal important. A good deal of the cloth which is made up into suits is known as shoddy, that is to say that material that has been worn before; old rags of all sorts and many other extraordinary things go to the making of this cloth. There are special factories to which rags are sent to be made up into shoddy. One might think therefore that this substance would be easily recognised under the microscope but it is not quite so easy as we shall see. Absolutely pure wool from the sheep giving the best quality wool is only used in the very finest and most expensive fabrics. In a great deal of really good cloth we may recognise other hairs besides those of the sheep and sometimes vegetable fibres find their way into good cloth by accident. A piece of suspected cloth should be cut off and separated as far as possible into its different fibres. In shoddy we shall find few long fibres and they will all be much torn for the reason that the rags from which the material is made are cut up in the manufacture. If we find cotton fibres, we may be certain that our specimen is shoddy, also if we can find fibres of many different colours, though the final dyeing may have disguised the fact that the fibres have originally figured in fabrics of various colours. Silk is one of the most important of all fibres capable of being woven into fabric. It is hardly necessary to remark that it is formed by the fully fed silkworm just before it turns into a chrysalis. A very large number of caterpillars spin silk but the majority of this silk is useless for commercial purposes. The silkworm gives off a double thread of silk from glands in its mouth and, at the same time, it gives off a sticky substance called silk glue which sticks the two fibres together, so that, to the eye at least they appear as one fibre.