42 MICROSCOPIC OBJECTfi- 



immersed in Canada balsam, which fills up all their cavities, 

 their appearance is most remarkably changed ; indeed;-.§o 

 great is the difference, that persons well acquainted with 

 the microscopic appearance of the hair in one condition 

 would not identify it in the other. The best example 

 illustrative of this fact is the hair of the Wapiti Deer. 

 To form an accurate notion of their real structure, they 

 should be examined in both conditions, and also as opaque 

 objects. A good microscopic investigation of the struc- 

 ture of hair is much wanted ; the essay by M. Breschet 

 entitled ' Nouvelle Recherches sur la Structure de la Peau' 

 may in the mean time be consulted with advantage. His 

 engravings are good. The felting properties of hair are 

 of vast importance in a manufacturing point of view. 

 The best means of determining the relative value of dif- 

 ferent kinds of hair and wool for these piirposes, is to 

 submit them to the microscope either as opaque or trans- 

 parent bodies ; if the latter, unmounted in balsahi, varnish, 

 or gum. - - 



The colour of the hau* is dependent upon the matter 

 contained within it, in the same manner as the colour of 

 the human skin is dependent upon the pigmentum under 

 it. Hairs that have become grey or white are found on 

 microscopic examination to be empty tubes, the pigmen- 

 tum having disappeared or its secretion ceased. 



Hair of the Bird-catching Spider {My gale avicularej of 

 South America, offers very great variety in structure. 

 That taken from the palpi is branched, and towards the 

 extremity the central stem enlarges, becomes fluted, and 



