5i8 'A Hcsmatozoon in Human Blood. Impart hi. 



The average diameter of the Hsematozoon, as usually found, is, as already stated, 

 about that of a red-blood corpuscle, and its average length about 46 times that of its 

 greatest width ; that is to say, its greatest transverse diameter is about -jj^Vti ^^ ^^ inch, 

 and its length about ^^\\x of an inch. These are about the measurements most frequently 

 met with, but I have occasionally seen specimens not more than half this size. The 

 largest specimen which I have measured was found to be slightly over B^^rVirth of an inch 

 in width, and about /g-th of an inch in length, whereas the smallest was only y^Voth of 

 an inch in width and y^sth of an inch in length : the relative proportion between the 

 length and the greatest width being as 1 to 45 in the largest and 1 to 56 in the 

 smallest ; the width therefore gaining somewhat in proportion to the length as the 

 total dimensions increase. 



From what has been above stated concerning the power of extension and contraction 

 possessed by the Haematozoon, it will be perceived that these measurements are subject to 

 variations during life ; and, as death may occur when the Filaria may happen to be in 

 either of these conditions, the relative proportion between the length and breadth may 

 then also be found to vary somewhat. 



In order to prevent misconception, it may perhaps be well to compare these measure- 

 ments with those of two well-known Nematode helminths which are occasionally found 

 in the tissues of the human body, viz.^ the Muscle-trichina and the Gruinea-worm, or 

 rather its contained embryos. Both of these parasites present a certain degree of likeness 

 to the Filaria described in this paper. The first-named is found in the muscular 

 tissue ; the second in the cellular tissue ; and the third in the blood. All three pre- 

 sent transverse markings, more or less evident; in the Gruinea-worm embryo they are 

 particularly distinct ; but beyond this feature the similarity between them appears to 

 cease. 



They differ from each other in size, in form, and in the relative proportions of 

 length to breadth — setting aside altogether the great difference which exists between 

 their minute internal organisation. 



As to size and form the Hsematozoon approximates more closely to the Filaria 

 medinensis or Gruinea-worm embryo, than to the larval stage of the Trichina spiralis, 

 though much smaller than either, especially in breadth. The average length of samples 

 of the former which I possess is g^-nd of an inch, and the breadth x^Vitj so that the 

 breadth to the length is as 1 to 31 : whereas the specimens of Trichina, with which 

 these comparisons were made, averaged -i^'On of an inch in length and y^xyth in width ; 

 so that they are only 28 times the length of their greatest transverse diameter. It 

 will be remembered that these proportions in the case of the Hasmatozoon have been 

 referred to as being on the average 1 to 46. 



A still greater dissimilarity between these helminths than the disparity in size 

 and relative proportions, is the totally different aspect presented by their anterior 

 and posterior extremities ; this is sufficiently evident without referring to the minute 



