PART III.] Transverse Strict seen tn the Living Worm. 515 



appearances presented by these Filarise, obtained from the same patient, will become 

 evident on perusal of a succeeding paragraph. 



One of the Haematozoa in this woodcut (No, 8) is seen to have preserved the 

 appearance presented during life, it having been instantaneously killed by holding 

 the slide over the fumes of osmic acid — by far the best method I know for preserving 

 the specimens. The blood should be quickly but evenly spread over the covering glass, 

 forming as thin a layer as possible ; the cover is then to be quickly inverted (before 

 coagulation sets in) over the mouth of a phial containing a 2 per cent, aqueous solution 

 of this chemical. When the preparation has turned somewhat brown, remove it and 

 place it on a slide, previously charged with a drop of a saturated solution of acetate 

 of potash or soda, when it is ready for mounting, and will keep, I believe, for an 

 indefinite period. 



(y^o account for the various appearances presented by these Hsematozoa before and 

 after death, which have been just described and figured, may possibly puzzle others as 

 it certainly puzzled me for over two years, although I was constantly in the habit 

 of examining specimens ; but, until their existence in the blood had been discovered, by 

 far the greater number of them had been dead, or nearly so, before they came under 

 observation. Having observed that the appearance usually presented by the Hsematozoa, 

 when recently withdrawn from the circulation, differed considerably from what was 

 observed after or shortly before death, it was determined to watch these changes from 

 beginning to end, and to note them as they occurred. With this object in view, a 

 specimen, which appeared to be well developed, was selected out of several found on 

 a quite recently prepared slide, a carefully corrected immersion -I" object-glass was 

 employed, and the examination continued for eight consecutive hours. 



At first the movements of the Hsematozoon were so rapid that little could be detected 

 in addition to what has been quite as distinctly seen with ^" glass, except that in certain 

 positions assumed by the worm, and in certain lights, extremely fine transverse striae were 

 observed quite distinctly. The existence of these strise had, on several occasions, been more 

 than suspected under the lower power (:^"), but they could not be satisfactorily demon- 

 strated. No attempt has been made to represent those fine markings in the woodcuts 

 as seen by such a comparatively low power as this, for it would only tend to mislead ; 

 to cut lines in wood only ^5^x)tt of an inch apart (which is about the distance between 

 the markings), when simply magnified 300 diameters, would be impracticable, and 

 even in the engraving, which represents the object as magnified by twice this power, 

 the distinctness of these markings is considerably exaggerated (Fig. 33, page 516). 



As the movements of the Filaria became a little slower, it was seen that the strise 

 were not on its outer coat, but confined to the body of the worm, and that the tail, 

 which almost always under the ^" objective looked like a lash, was not so in reality, 

 but that, every now and then, it could be seen flapping against the corpuscles like a 

 fin — sometimes vertically, sometimes horizontally, and then becoming folded upon itself 



