PART III.] Enclosure of the Worm in a Tube closed at both Ends. 517 



which the preparation is placed, will generally cause a separation between the sac 

 and its contents, as was actually produced in the specimen marked 4 in the same 

 woodcut. 



The Hsematozoon may, therefore, be said to be enveloped in an extremely delicate 

 tube, closed at both ends, within which it is capable of elongating or shortening itself. 

 This envelope, like the sarcolemma of muscular fibres, is without any visible structure, 

 is perfectly transparent, and, but for the difference between it and the fluid in which 

 it is immersed in its power of refracting light (which allows of its margins or folds 

 being brought into view), and for the phenomena so strikingly evident when the Filaria 

 alters its length, its tubular character could not be demonstrated. 

 /^The fact of its being thus enclosed seems to show that in the present stage of its 

 existence, the " home " of this Filaria is in the blood ; it has no visible means of per- 

 forating the tissues : moreover, although constantly observed to be in a state of great 

 activity, it does not seem to manifest any special tendency to migration, and is 

 apparently dependent on the current of the blood for its transference from place to 

 place ; its movements, therefore, within this enveloping tube appear to be as limited 

 as those of any other animal enclosed within a sac. 



As has been already stated, a short chain of aggregated molecules, probably repre- 

 senting the rudiments of an intestinal canal, is frequently seen towards the centre 

 (Fig. 33, 1), but the rest of the entire length is at first uninterruptedly clear, although 

 not transparent. But during the time the details described in the preceding paragraphs 

 were observed, and they became more and more evident as the activity of the Hsematozoon 

 diminished, the appearance throughout became granular or rather molecular. A bright 

 spot also became very evident at the terminal point of the anterior portion, which, as 

 already remarked, is extremely suggestive of an oral aperture, and immediately below 

 this a somewhat elongated vacuole. From this downwards, until about the junction of 

 the middle with the lower third, or perhaps a little nearer the middle, a more or less 

 clearly differentiated oesophagus (?) became likewise discernible, and appeared to have a 

 csecal termination ; but beyond this, until the caudal extremity was reached, the continua- 

 tion of the digestive tract was less clearly defined (Fig. 33, 3). 



It then became too dark to continue the observation, and by the next morning the 

 Filaria had become uniformly molecular, all appearances suggestive of internal organs 

 having vanished, although it still continued to coil itself languidly amongst the blood 

 corpuscles. 



Such is the minute anatomy of the Hsematozoon as far as I have been able to make 

 it out. What has here been recorded has now been repeatedly observed, and may be 

 observed by any one possessing a good I" or xV" immersion lens and a microscope provided 

 with good arrangements for illumination. The simple detection, however, of the Hsema- 

 tozoa, when present in the blood, is simply a question of patience, and not dependent on 

 any special perfection in the magnifying powers employed. 



