6o6 Microscopic Organisms in Blood of Man and Animals. [part hi. 



They may readily be preserved by spreading out a thin layer of the blood containing 

 them over a thin covering glass and inverting it over a weak solution of osmic acid. 

 The preparation should be removed as soon as it presents a dry, glazed appearance, 

 and may be thus mounted in the dried condition or in a saturated solution of acetate 

 of potash. I have, however, never been able to detect the flagellum in such a preparation ; 

 apparently the refractive index of the substance forming the flagellum and that of the 

 serum approximates so closely that the last can only be detected when creating a current 

 by its movements. The "body" remains nearly as translucent after the action of the 

 osmic acid-fumes as it was in the living condition, so that the presence of the protozoa 

 in such a preparation may readily be overlooked owing to the absence of any movements 

 to direct attention to them. 



When, however, a preparation of blood of this kind is dried in the manner ordi- 

 narily suggested for preserving specimens of blood, and especially if a little of a weak 

 solution of aniline-blue be afterwards poured over the dried slide, the body of the 

 protozoon will present a very different appearance. It will be found to have contracted 

 irregularly, and to manifest a somewhat granular and shreddy appearance, suggestive of 

 a coagulated, fibro-albuminous substance. The " body " portion becomes flattened to- 

 wards its middle to double its original width, and both ends become almost acutely 

 pointed. The flagellum part is only visible for about half its true length, and this 

 portion of it appears to consist of the same substance as the body. Possibly the now 

 invisible portion of the flagellum may consist of a substance slightly different from that 

 of the body ; or may have been retracted during the drying. I have made micro-photo- 

 graphs of slides prepared in both ways, hoping that possibly an image of the entire 

 lash might thus be obtained, even though the eye could not distinguish any, but have 

 not succeeded, notwithstanding that the rays of light were caused to pass through 

 glass of various colours.* The logwood solution recommended by Koch for this purpose 

 also failed in my hands. 



It is impossible to secure accurate measurements of these organisms during the 

 period of activity, nor of the lash at any time, seeing that the latter becomes for the 

 most part invisible in preserved preparations. The body portion, however, may readily 

 be measured after they have been killed by means of osmic acid. The width of the 

 anterior half, or body portion, averages -8 to \fi, or precisely that of ordinary blood- 

 bacilli, and its length from 20 to 30/i, or an average of 25//,. The flagellum, so much 

 of it as is visible, is somewhat of the same length, so that the total length of the 

 organism equals about 50yu., or about 5^". The lash, however, may be considerably 

 longer than this, as the slope from the body portion is very gradual, and when the eye 

 follows it to the bounds of visibility an impression is conveyed that there may be still 

 more of it, beyond the power of either Koss's ^^^ ' or Powell and Lealand's ^V" to reveal. 



They are not very sensitive to the action of re-agents ; a weak solution of 



* Facsimiles of two of these micro-photograpLs will be found in Plate XLIIIJ 



