70 G. F. DOWDESWELL. 



forms of Schizopli)'tes^ are present, iu some cases in great 

 numbers. 



Per this examination I have mainly followed the methods 

 introduced as already mentioned by Drs. Weigert" and Koch as 

 follows : — A drop of blood is spread in as thin a stratum as 

 possible on a cover-glass, rapidly dried, and strongly heated over 

 the jiame, in order to coagulate and fix tlie albumen ; it is then 

 treated for some time with a strong aqueous solution of one 

 of the aniline dyes, which is drained off, the preparation rinsed 

 with alcohol, either dried or treated with oil of cloves, and 

 mounted in Canada balsam. I have not found the use of the 

 oil of cloves necessary ; it decolorises the Bacilli, which are never 

 too deeply stained. If the blood is in a sufficiently thin stratum 

 this is all that is requisite. The Bacilli which occur in these 

 cases are so characteristic that when sufficiently stained it is 

 impossible to mistake them, or to confound portions of the 

 tissues with them. The preparations may, however, be treated 

 for a very short time with a weak solution of acetic acid (one 

 per cent.) or of potassic carbonate (five per cent), preferably the 

 latter, for I have frequently found the former decolorise the 

 Bacilh almost instantaneously ; in either case the preparation is 

 then washed first with water then in alcohol and mounted in 

 Canada balsam. 



To prepare the different organs for microscopical examination 

 on the animal being killed, they are at once excised and placed 

 in strong alcohol.^ When sufficiently hardened sections are 

 cut ; they are then stained by immersion for some time in a 

 strong aqueous solution of one of the aniline dyes. It is then* 

 found that any Bacteria in the preparation and the nuclei of the 

 tissues are alike stained with little distinction, but by vv'ashiiig 

 in water and treating with a solution of sodic or potassic car- 

 bonate the tissues become pale, and the staining of the nuclei 

 fades, while the Bacteria, having a stronger affinity for the 

 aniline colours, are less affected, and thus strongly differentiated. 

 The strength of the alkaline solution and the length of time the 



* Bacteria is the general, though incouvenient, term here for the whole 

 group of these organisms, otherwise named Microzymes, Microphytes, or 

 Protophytes ; in Germany, Schizophytes or Schizomycetes ; in France, 

 Bacteridie, and various other names; following P. Cohn, they are now 

 generally divided into three principal genera : Bacteria, Bacilli, and Micro- 

 cocci. 



^ Koch, loc. cit. ; Weigert, ' Virchow's Archiv f. Path. Anat., &c.,' for 

 May, 1881. 



* If absolute alcohol is used, the red blood-corpuscles are preserved in the 

 vessels, by which a natural injection, as it were, is made ; and in many 

 cases, especially in exceedingly thin sections, the preparation is much 

 improved ; of less strength than about 90 per cent., alcohol dissolves the 

 colouring matter of the corpuscles. 



