108 MICROSCOPIC OBJECTS. 



Spicula $c. See figs. 107 and 108. 



Starches. Many of these may be mounted in silicate of 

 potassa, care being taken to moisten the starch first, or air- 

 bubbles will be formed, which are difficult to get rid of in this 

 substance without the use of the air-pump ; if required for the 

 polariscope, balsam is best. For other remarks, see the starches 

 (figs. 53, 54, &c.). 



Insects, parts of, &c., are best when mounted in balsam, 

 although some of the smaller ones perhaps exhibit their struc- 

 ture better when mounted in acetic acid, 1 part acid to 2 parts 

 water ; they may be mounted in one of Pumphrey's ebonite 

 cells, or in a cell made of the india-rubber cement ; in both 

 cases this is the substance with which to seal the cell. For 

 other information on mounting &c., see Insects. 



Palates, or tongues of the Gasteropoda, a class belonging 

 to the Mollusks, are generally dissected from the animal, 

 cleaned with potass, washed, dried, and mounted in balsam ; 

 they are then generally seen under the polariscope. Some, 

 like the whelk's tongue, require to be slit up the centre, 

 spread out and dried ; they show well when mounted in gly- 

 cerine. 



Zoophytes, Rotatoria, fyc. show best when mounted in a 

 fluid as nearly as possible like their native element. 



White slabs to be used for dissections &c. are made of the 

 white gutta-percha enamel (sold as a tooth-stopping) mixed 

 with white wax; after this substance is run out into slabs 

 about the T V of an inch in thickness, they may be cut up and 

 used at the bottom of the cells when it is required to exhibit 

 any particular dissection in its natural position; for rough 

 purposes ordinary gutta percha may be used, mixed with wax 

 in the same manner. For dissections under water the gutta- 

 percha and wax substance must be melted at the bottom of a 

 deep white vessel ; the porcelain dishes that photographers use 

 will do for this purpose ; a common dish, if deep, may be used. 



In staining tissues the germinal or growing matter is 

 coloured, and the formed or mature matter is not. But, then, 

 do not use Judson's dyes ; they dye every thing : see Demodex 

 (fig. 173), Eritozoa, &c. 



