PART iii.^ Human and Canine Filaria Sanguinis different from each Other. 537 



Whilst making a microscopic examination of some gland tissue from the mesentery 

 of a pariah dog (last July), I observed that the sanguineous fluid squeezed out of the 

 preparation on the slide contained numerous minute nematode worms in a state of 

 great activity, and presenting at first sight a marked resemblance, both as to the 

 character of their movements and their size, to the Haematozoon referred to above as 

 existing in human blood. I had for a long time been desirous of obtaining living 

 specimens of a canine Haematozoon so as to be able to institute a comparison between 

 this kind and those found in man, although I had not entertained any very sanguine 

 hope of being able by this means alone to pronounce definitely as to the identity or 

 otherwise of the two parasites, for it has long been known that the embryos of many 

 Filariae of widely differing size and habitat present no appreciable difference either of 

 size or form : instances being known of the young of even a totally distinct group of 

 nematodes being nevertheless so like as to be miscroscopically undistinguishable the 

 one from the other. 



It was, however, very evident that should any anatomical or other marked 

 discrepancy be observable in parasites subject to the same influences, there could be 

 no difficulty in coming to a very positive opinion on the matter. With reference to 

 the particular Hsematozoa under consideration, the anatomical disparities are so 

 unmistakable that I have not the slightest hesitation in pronouncing them to be 

 totally distinct parasites. Dr. Douglas Cunningham, who has repeatedly and most 

 carefully examined both kinds in the living state, is equally satisfied on this 

 point. 



For the sake of comparison, figures have been introduced of these human and 

 canine Hasmatozoa (Plate XXXVIII, Figs. 1, 2), from which it will be perceived that they 

 correspond very closely as to size : the average measurements of the latter may be 

 stated as about y^^th of an inch from end to end, and about x-sVuth at the widest 

 part, the average dimensions being slightly smaller than those yielded by the human 

 parasite. The relative proportion of the breadth to the length in the canine variety is 

 about 1 to 50 the tail occupying about ith or |th of the total length — the relative pro- 

 portions also diff"ering somewhat from those of the young Filaria sanguinis hominis* 

 The measurements and proportions, however, vary to some extent according as the 

 parasite is measured in the extended or the contracted condition. 



I can detect no indication whatever of this canine haematozoon being enclosed 

 within any enveloping tube, such as the structureless, hyaline, tubular sac, enclosing 

 the human parasite, and within which the latter parasite can be observed to contract 

 and elongate itself — no portion of it being structurally adherent to the enclosing sac. 



* On one occasion I detected a specimen in the blood of a dog yielding much lower measurements, viz., ^-f^ 

 of an inch in length by ^^^ »* ^^ ^"^^ ^* *^® widest part, the breadth being to the length as 1 to 34. In this 

 resnect also the canine embryo parasite differs from the Filaria sangvinis hominis, as the proportion between the 

 breadth and the length in the smaller specimens instead of diminishing, as in the canine variety, increases 

 considerably— the smallest specimen which was measured of the human variety having been j-^^ of an inch at 

 the widest part, and y^^ of an inch in length ; the width being to the length as 1 to 56, whereas in the larger 

 specimens it was found to be as 1 to 45. 



