512 A Hcematozoon in Human Blood. [part hi. 



It must not be supposed that the Filarise are to be detected by taking a mere 

 peep through the microscope ; sometimes, certainly, I have observed one, or two even, 

 in the first field examined ; but this is by no means usual, and their detection often 

 demands considerable patience. Each slide will require about a quarter of an hour 

 before it can be satisfactorily explored ; any one who imagines that they can be detected 

 with the same ease as a white-blood corpuscle had better not make the attempt. 



Several slides may have to be examined, and it may be necessary to make a fresh 

 puncture, for I have found the Hsematozoa to be absent in several slides obtained 

 from one finger, but present in all the slides obtained from another at the same time ; 

 whereas on making a fresh puncture in the finger where none had been found at 

 first, it was ascertained that they were equally numerous in both. This is possibly 

 accounted for by the little orifice made having become plugged by fat, etc, so that 

 the blood s queezed through had to some extent been filtered, for although this microscopic 

 Filaria can pass through any channel permeable to a red-blood corpuscle, still, when 

 it is considered that the length of the former is nearly fifty times its diameter, the 

 wonder is that they are not more completely prevented from escaping through so 

 fine an orifice even when perfectly patent. 



The search should not be undertaken with too high a magnifying power, but it 

 should be sufficiently high to define the outline of a red-blood corpuscle quite distinctly. 

 I have found that a good two-thirds of an inch objective answers the purpose of a searcher 

 admirably ; it embraces a tolerably large area so that the preparation can be examined in 

 a comparatively short time ; but care should be taken to keep the fine adjustment 

 screw constantly moving, so as to examine the deeper as well as the superficial layer 

 of fluid in each field as it passes under observation. Should anything unusual be 

 observed, the low power must be replaced by a y' or, better, a \' objective.* 



In order to keep the active Haematozoon under observation for some hours, a 

 camel-hair pencil, dipped in a solution of Canada-balsam, or mastic in chloroform, should 

 be passed along the edges of the covering glass, so as to prevent evaporation and the 

 formation of air spaces in the preparation. 



The appearance presented by the Haematozoon when first seen among the blood 

 corpuscles, in the living state, will not readily be forgotten, and cannot possibly be 



* It may -seem superfluous to draw attention to the similarity which exists between some vegetable fibres 

 and some of the miscroscopic " FilariiE," when the latter are not alive ; nevertheless a very good objective is 

 frequently required to distinguish them with certainty, as any one may prove for himself by subjecting the 

 torn fluffy edges of a piece of blotting-paper to miscroscopic examination. Filaria-like fibrils will fi-equently be 

 found. 



A mistake of this kind is referred to by Leuckart as having occurred quite recently. A paper was 

 published announcing the discovery of a Filaria-like Mematode in the intestines, blood and tissues of a patient, 

 which was expected to prove as dangerous to life as the Trichina spiralis. These parasites subsequently proved 

 to be nothing more than vegetable hairs ! — " Die Menschlichen Parasiten," Vol. II, part 1, p. 151. 



