40 PRACTICAL HISTOLOGY. 



thick ; the ends of the cord are united so as to form 

 a ring, and this is placed on the middle of a clean 

 glass slide. A drop of water is put into the centre 

 of the ring ; this is for the sake of keeping the at- 

 mosphere of the chamber rnoist ; but the object may 

 be equally well effected by breathing into the space 

 as it is being covered over. The object is prepared 

 on the centre of a clean cover-glass, which is then 

 inverted over the ring, so that the preparation is 

 dependent into the chamber, and, whilst freely 

 exposed to the air in this, is entirely protected from 

 evaporation and may be readily examined through 

 the cover-glass, to the under surface of which it 

 remains adherent (Fig. 10). 



Fig. 10. 



To investigate the action of chloroform vapor it 

 is necessary to have some means of passing this into 

 the moist chamber, whilst the drop of blood is under 

 observation. For this purpose a slide is employed 

 (Fig. 11), to which a piece of small glass tubing has 

 previously been fixed by means of sealing-wax, and 

 the ring of putty is so placed as to include the end 

 of this, a small interval being left at the side of the 

 tube to afford an exit for the vapor. The slide is 

 then clamped on to the microscope stage (as in Fig. 



