222 FIXING AND STAINING BLOOD-FILMS. 



This is simply the most rapid dinical form of the method. 

 Any other acid stain which is soluble in alcohol and not precipi- 

 tated by sublimate may be used instead of eosin, and the stain 

 may be omitted from the fixative altogether, so that the cover-glass 

 specimen, after fixation in the alcohol-ether-sublimate, may be 

 stained in any way that is desired. 



The method is no less useful for fixing pus, sputum, and any- 

 thing else which can be spread in a film ; only with these it is 

 generally advisable to prolong the fixation. The cover-glasses 

 used must be scrupulously clean. The simplest way of insuring 

 this is to put them for a few minutes in glacial acetic acid, then 

 wash them with plenty of water so as to remove the acid tho- 

 roughly, and dry them with a fine handkerchief. A large quantity 

 should be treated at one time and stored up. 



The thinner the film the better the fixation. As it is not pos- 

 sible in specimens mounted in balsam, by whatever method, 

 exactly to reproduce the appearance of fresh corpuscles, as seen in 

 freshly drawn blood, it is desirable to control balsam preparations 

 by examining fresh blood, or, still better, by pricking the finger 

 through a drop of 2 per cent, osmic acid solution and examining 

 the preparation thus made in a fluid mount. This is especially 

 desirable where the red corpuscles are altered in shape to a slight 

 extent ; greater degrees of poikilocytosis can easily be made out 

 in balsam preparations. 



Plant Chemistry. — Of the seventy elementary substances 

 recognised by chemists, only thirteen contribute to the formation 

 of vegetable substances. Out of this baker's dozen all the varied 

 forms of leaf, flower, and fruit are fashioned. Of these thirteen 

 organic elements, three make up more than nine-tenths of all cul- 

 tivated plants. These are carbon, oxygen, and hydrogen — carbon 

 and water. While these make up the largest part of plants, they 

 are not classed as manures, because they are not applied by hand, 

 but come to the plant from the atmosphere in the form of carbonic 

 acid and rain. They are Nature's free gift to plant life, and are 

 borne on the wings of every wind that blows and the clouds that 

 float dXoiX..— Journal of Horticulture. 



