i6o 



HARD WICKE ' 6" S CIENCE - G O SSI P. 



of pumice stone, the surface of which is chased into 

 quadrangular facets or dice, and which has been 

 christened the Patent Chequered Pumice Tablet. 

 In this little article the practical microscopist will 

 find a true friend. All he has to do, whilst washing 

 the hands, is to use this little scrubber with its 

 faceted surface well covered with soap, and he will 

 find all stains and smears vanish under its action, as 

 if by magic. Such, at any rate, is my experience, 

 and I have been so well pleased with it that I have 

 thought it worth while thus to bring it under the 

 notice of my fellow-workers, in order that they may 

 share the satisfaction which I have experienced from 

 its use. — Dr. M. 



Another Method of Staining Microscopical 

 Specimens. — Dr. G. Brosicke, of Berlin, recom- 

 mends a combination of osmic acid and oxalic acid 

 for staining the tissues, instead of osmic acid alone. 

 Small pieces of the tissue, or prepared sections, are 

 placed for an hour in one per cent, osmic acid solu- 

 tion, and then carefully washed to remove all super- 

 fluous acid. They are then immersed for twenty-four 

 hours or longer in a cold saturated aqueous solution 

 of oxalic acid (one to fifteen), and are ready for 

 examination in water or glycerine. The result is that 

 while certain substances, such as mucin, cellulose, 

 starch, bacteria, the outer coat of certain fungi, &c, 

 are scarcely at all coloured, other tissues, such as the 

 vitreous humour, the substratum of the cornea, the 

 walls of the capillaries, and various intercellular con- 

 nective tissues, appear of a bright carmine ; and 

 muscular fibres, tendon, hyaline cartilage, the inter- 

 fibrillary substance of decalcified bone, and most of 

 the tissues rich in albumen are stained a darker 

 carmine. The grey substance of the central nervous 

 system, most nuclei, and many cells assume a dark 

 Burgundy red tint. In all these cases, however, each 

 particular tissue is stained a slightly different shade, 

 so that it can be readily distinguished from its neigh- 

 bours. None of the objects treated by this method 

 swell up, or exhibit signs of internal coagulation. 

 The oxalic acid produces darker or lighter shades in 

 proportion to the length of time the specimen had 

 previously been immersed in osmic acid, and if the 

 latter has once completely blackened the tissue, the 

 oxalic acid is powerless afterwards to redden it. 

 Mixed solutions of osmic and oxalic acids stain pro- 

 portionally to the relative strength of each. The 

 chief drawback to this method is the small penetrating 

 power of osmic acid, which prevents the whole thick- 

 ness of a specimen from being equally stained. 



"Centerer" for Slides.— In your September 

 number, 1875, y° u inserted a sketch of my " centerer." 

 As I have altered and, I believe, improved it, I enclose 

 a sketch of what I now use. The shaded part is a piece 

 of wood about j, inch thick, screwed on the bed, 

 which is about \ inch thick ; sycamore is a good 

 wood for it. I use a piece of paper about 2 inches 



long, and can thus have two different-sized holes 

 punched, which I place under the centre of the 

 slip. Under this I have a similar piece with two 

 colours on each side, so that I can use either. I find 

 black, white, blue, and red useful. The advantages 



Fig. 134.— Improved Centerer for Slides. 

 of these alterations are that from the narrow neck 

 and the shortness of the paper the glass is more easily 

 handled, whilst we have more varieties on the same 

 paper of colours or holes. I use a round button, 

 putting the screw about ^ inch from the centre.— 

 W. Locock, Clifton. 



Lead Cells.— Mr. M. A. Veeder, of Lyons, New 

 York, recommends cells made from the thin sheets 

 of lead with which tea boxes are usually lined. The 

 depth of the cell may be increased, by placing several 

 lead rings one upon another. Shallow cells may be 

 formed with the greatest ease in this manner. 



ZOOLOGY. 



Mistakes of Instinct. — As a contribution to 

 this subject, I may mention a failure of instinct in 

 Anthocharis Carda/nines, which has just come under 

 my observation. I always find the eggs here laid on 

 Cardamine pratensis, and always on the pedicel of the 

 flower. When the flower-bud is very small, it is 

 almost sessile ; but still the egg will be found so 

 placed as to avoid the floral envelopes, which being 

 very caducous will have fallen before the egg is 

 hatched, while it is the growing seed-pod which the 

 young larva wants to get at. I had some A. Car da- 

 mines this year which were bred and laid eggs in a 

 gauze cage upon cut flowers of Cardamine, and in 

 one instance the egg was deposited upon the sepal of 

 the flower, where in the natural course of things it 

 must have perished. — J. A. Osborne, M.D., Mil/ord, 

 Letterkenny. 



f Simulation of Death by Insects. — In an 

 interesting paper read not long ago before the Ento- 

 mological Society, the simulation of death so frequently 

 observed among insects was regarded not as an in- 

 tentional stratagem to escape danger, but as a species 

 of catalepsy due to terror, and was, if I mistake not, 

 compared to the so-called fascination which certain 

 birds and small mammals experience in presence of a 

 serpent. It seems to me that the tendency to such 

 simulation in different species is, roughly speaking, 



