v.] METHODS OF INOCULATION. 47 



course necessary to keep the specimen heated up to the 

 desired temperature. 



The simplest method consists in sowing the organisms on 

 a suitable nourishing material in a small glass cell, fit to be 

 placed on the stage of a microscope and to be there observed 

 even with high powers, similar to those cells which Koch has 

 used in his studies on bacillus anthracis. Such a glass cell 

 consists of a glass slide, in its centre a concave pit, not too 

 large, and capable of being quite closed up by an ordinary 

 cover-glass, the edges of which fasten by means of clean 

 paraffin or olive oil. Place with a clean needle a speck of 

 spleen pulp of an animal dead of anthrax into a drop of 

 nourishing material, fluid or solid, on the centre of a clean 

 cover-glass, the edges of which have been prepared as just 

 mentioned, and fasten this on the above slide so that the 

 specimen faces .the concave pit : expose this so prepared 

 specimen to a constant temperature, either by placing it in 

 the incubator and examining it with the microscope from 

 hour to hour, or on the warm stage (Strieker, Ranvier) used 

 in histological work for directly observing the influence 

 of temperature on the various cells and tissues ; or, place 

 it simply on the stage of the microscope and expose the 

 whole (i.e. microscope and all) in a suitable warm chamber 

 (after Klebs), but so that the chamber allows light to pass 

 by means of a small window to the mirror of the 

 microscope, while the eyepiece is so arranged as to project 

 through a hole in the upper wall of the chamber. The plan 

 which I generally follow is with slight modifications that 

 of Koch. 



A glass cell (Fig. 10) is made 1?y cementing a glass ring, 

 f-g inch in diameter and about \-^ inch high, on to an 

 ordinary glass slip. The chamber of this cell is well cleaned 

 with absolute alcohol. A thin cover-glass, square or round, 



