( 18 ) 

 PROGRESS OF MICROSCOPICAL SCIENCE. 



Structure of the Mole's Snout. — Tliis is given very fully in the last 

 part of Max Sclinltze's ' Archiv,' in a paper by Herr Th. Eimer, of 

 Wiirtzburg,* wliich is briefly abstracted in the ' Lancet.' The 

 muzzle of the mole in part supplies the place of its extremely 

 defective organ of vision. The sensory area is situated at its anterior 

 extremity, and presents even to the naked eye a jjapillated surface. 

 When examined with the microscope, the papillae are found to be low 

 elevations varying from a tenth to a fifth of a millimetre in height. 

 The papillse are composed of epithelium, which not only projects from 

 the surface, but dips into the corium : the cells occupying the little 

 fossa in the corium are ribbed cells. Each papilla is traversed from 

 base to apex by an hourglass-shajied canal, the perij)hery of which is 

 of course bounded by the ej)ithclial cells. The canal is filled by a 

 structureless homogeneous mass, probably of the nature of mucous 

 tissue. The nerves traverse this tissue, and end by free extremities in 

 the outer division of the hourglass-like cavity, which Eimer terms the 

 tactile cone. The disi^osition of the nerves is very peculiar. If the 

 skin of the snout be treated with chloride of gold, the corium is seen 

 to be richly supplied with a plexus of medullated nerve-fibres. From 

 these, small fasciculi containing twenty or more are given off, which 

 rim to the base of the papillae and enter the inferior cone, at the same 

 time losing their medullary layer. They then appear to arrange 

 themselves in the form of a circle, presenting in transverse sections 

 very much the appearance of the copper wires in the electric cables. 

 As the fibres ascend the tactile cone towards the surface of the skin, 

 they are connected by a slight nodal enlargement or varicosity with 

 each successive tier of cells, terminating as near the surface as the 

 third or fourth epithelial cell-layer. Here and there a nerve-fibre 

 (cylinder axis) runs amongst the epithelial cells of the papillae ex- 

 ternal to the cone. As the number of papillae is about five thousand, 

 and as about twenty nerves enter each tactile nerve-cone, the total 

 number of fibres must amount to about one hundred thousand, and 

 their very superficial termination is a matter of great interest. 



Various Investigations on the Dust of the Air. — We have of late had 

 various reports on this subject. The first is by Mr. J. Sidebotham, 

 and was read before the Manchester Philosophical Society at a late 

 meeting. It appears that while travelling by rail between Saltley and 

 Camp Hill, he spread a paper on a seat of the carriage, near the open 

 window, and collected the dust that fell upon it. A roiigh examina- 

 tion of this with the |rds power showed a large proportion of frag- 

 ments of iron, and on api)lying a soft iron needle he found that many 

 of them were highly magnetic. They were mostly long, thin, and 

 straight, the largest being about ^^^^ ^^ ^^ inch, and, under the power 

 used, had the appearance of a quantity of old nails. He then with a 

 magnet separated the iron from the other particles. The weight alto- 



* Band 7, Heft 3. 



