626 Microscopic Organisms in Blood of Man and Animals. [part hi. 



2(n)tr' ('012 mm.) ; whilst the average measurements of three ova in which the embyros 

 were visible = V|/ (-037 mm.) by ylxy" ('030 mm.). 



When the latter, after having arrived at this stage of development, are examined 

 during life, it is in many instances difficult to state whether they are to be considered 

 as freed embryos or not, as the " egg-shell '" has become so extremely attenuated and 

 translucent as only with difficulty to be distinguished. By pressing the covering glass 

 firmly the sac may often be ruptured. It, however, appears probable that, even when 

 the embryo acquires worm-like appearances, the envelope is not lost in this species so 

 long as it continues in the blood. 



It is of importance to bear this in mind, as, contrary to what is seen with regard 

 to the nematoid hsematozoa of dogs, the embryos in the blood of man are each con- 

 tained in a translucent cgecal tube. This tube is readily recognisable during life 

 whenever the embryos can be properly observed in fresh clear serum, as also in spirit- 

 preserved preparations. I possess at the present time specimens thus preserved of 

 both species, one being contained in blood removed from the heart of a person who, 

 during life, was known to harbour hsematozoa, and the other obtained from the blood- 

 vessels of a dog similarly affected. In not a single instance have I been able to 

 distinguish the least trace of an enveloping tube in the latter, whereas in the former 

 this tube can be clearly demonstrated in the majority of instances. Hence, notwith- 

 standing their almost complete accord as to dimensions, the character just referred to 

 is sufficient to distinguish slides prepared from either of these two specimens. A like 

 distinction has been ascertained to exist between the two kinds of embryo-filarise in 

 China by Dr. Manson ; but, according to Dr. Sonsino, those of Egypt, and apparently 

 those of the Brazils, do not present this distinguishing feature. As may be recollected, 

 it was mentioned that a distinction also exists between the disease with which the 

 human hsematozoon is associated in the different countries, — not a great difference 

 certainly, but, nevertheless, one which should be borne in mind when deciding as to 

 specific distinctions between the parasites. 



It must also not be forgotten that the inhabitants of Brazil and of certain parts 

 of Africa are, as has been known for at least a century, peculiarly liable to be the hosts 

 ' of tissue-parasites. The minute thread-like sub-conjunctival filaria {Filaria loa), for 

 example, though from two to six inches in length, has never been accurately described, 

 and its precise thickness is not known yet, although it was discovered by Bajon so 

 long ago as 1768,* and has since been frequently observed beneath the skin and 

 conjunctiva of negroes and other persons. M. Guyon brought it before the notice of 

 the French Academy in 1838, and again in 1864. On the former occasion, the 

 specimens measured 30—40 mm., but the helminth described in 1864 was 150 mm. in 

 length. It is not quite clear that they belonged to the same species. It is not 

 impossible that the embryos discovered by Dr. O'Neill f in a disease of the skin 



* Cvniptes Rendus, t. lix, 1864, p. 745. 

 t The. Lancet, Feh. 10, 1875, p. 265. 



