26 JOURNAL OF THE [April, 



covers are laid by us a certain time, say five seconds, on the 

 mounting-plate, heated at the height of five centimetres above the 

 miniature Bunsen burner with a flame one centimetre in height ; 

 or directly over this flame, at a certain height for a iew seconds. 

 The heating in this way is far more uniform than by the common 

 method, the films are well dried but not roasted, and more satis- 

 factory results maybe expected in the subsequent staining. What 

 could be a more disproportionate, wasteful, and absurd process 

 than the common one of warming a tiny thin cover, of the size 

 of one's little finger nail, over a rush of flame six or seven inches 

 in height ! 



III. Staining- Flask. 



The staining of films which have been dried upon covers, 

 such as bacteria or blood corpuscles, especially when heat is re- 

 quired, often leads, by the common methods, to imperfect or 

 erroneous results in inexperienced hands. Sometimes the stain, 

 after having been heated up in a test-tube, is thrown in a watch- 

 glass, and the cover floated upon it, film downward (Gibbes' 

 method). 



The usual method is to hold the cover, with the film uppermost, 

 between the fingers or in a forceps, add a drop or two of the 

 stain, and heat over a low flame until steaming vapors rise from 

 the stain. Though simple, this is troublesome where many films 

 need staining at one time or in succession. There is also a ten- 

 dency of the stain to dry in an overheated ring around the edge 

 of the cover as well as to deposit granules of color, which, in 

 some cases, adhere firmly to the film and cannot be removed by 

 washing. This is more likely to occur when long heating is needed 

 to stain the object to sufficient depth of color ; the little drop 

 evaporates rapidly, and constant attention is needed to keep it 

 supplied with fresh additions of stain. 



In place of these methods, the following simple apparatus has 

 been in satisfactory use in our laboratory for many years. It 

 consists of the following parts : 



I . A tight coiled spring (Fig. 2, A), as a cover-holder, in which 

 a large number of thin covers may be clamped by insertion be- 

 tween successive coils. It is made from a spring of fine brass, 

 copper, or steel wire, not coarser than No. 26 gauge, wound on a 

 one quarter inch mandrel. It is best made from fine platinum 



