ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 299 



table b carried on a horizontal arm c, which is fastened to the right- 

 hand corner of the stage of the Microscope by a screw passing through a 

 hole in the stage and provided with a nut e. The glass disc is centered 

 on the circular table and fastened with a pair of spring clips //placed 

 near the centre. The table, carrying with it the disc, is rotated by a rack 

 and pinion or rather cog-wheel movement, worked with the right hand by 

 means of a milled head d placed underneath. The concentric circles of 

 sections are brought under the tube by the movement of the horizontal arm, 

 by means of which the centre of the revolving table is brought nearer to or 

 carried further away from the centre of the stage. 



"Warm and Cold " Stages." — In studying the anatomical elements of a 

 warm-blooded animal, and other phenomena which naturally occur under 

 the influence of a temperature considerably above that of the surrounding 

 air, it is necessary to have some means of maintaining a condition as to 

 temperature resembling that of the living organisms, or even, as in the 

 experiments of Dr. Dallinger, described supra, p. 185, of raising the tempera- 

 ture to an abnormal point. We summarize here some of the princij)al 

 suggestions that have been made for this purpose (as well as for producing 

 cold), excluding such as have previously been recorded in this Journal. 



A very crude process described by Rasjpail * was to put the object in 

 water in a watch-glass on the stage, a spirit-lamp being placed beneath it, 

 which served both for heating the water and giving light to the object. The 

 objective was covered by the globular end of a thin glass tube, which dipping 

 into the water, prevented the obscuration of the object by vapour and pro- 

 tected the objective. Harting,f following, but not quoting, Goring and 

 Pritchard if proposed to substitute for the glass tube a brass one, closed by 

 a plane plate of glass. Schacht § also heated the slide direct by a minute 

 wax taper placed (for short periods) below the opening in the stage. 



Apart from these methods, four different principles have been adopted 

 for heating microscopic objects : (1) by hot air ; (2) by electricity ; (3) by 

 conduction through metal plates ; and (4) by water. 



1. Air. — This is perhaps the least convenient medium of all for heating 

 microscopic objects. 



Prof. G. Fritsch commends Dr. Senarmonfs |1 apparatus as a very simple 

 and handy stage, which " in its arrangement is to be preferred to those of 

 Max Schultze and Strieker." It consists (figs. 48 and 49) of a hollow 



Fig. 48. 



box of tin K, open at one end, and having at the other an aperture in the 

 lower surface, to which is attached a cylindrical tube of mica. The box is 



* Kaspail, L. V., ' Nouveau Systeme du Chimie Organique,' 2n(l ed., i., 1838, pp. 222-3 

 (1 fig.). t Harting, P., ' Das Mikioskop,' 2nd ed., ii., 1866, pp. 146-7 (] fig.). 



X Goring, C. E., and Pritchard, A., 'Microscopic Illustrations,' 1830, pp. 55-6 

 (2 figs.i. § Schacht, H., ' Das Mikroskop,' 3rd ed., 1862, p. 79. 



II Bericht u. d. Wiss. Instrumente a. d. Berliner Gewerbeausstellung im Jahre 1879 

 (L3wtnherz), pp. 305-6 (1 fig.), and pp. 355-6 (1 fig.). 



X 2 



