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



will be visible, rendering it extremely difficult or impossible to state precisely what 

 it is that actually does take place ; at least hitherto I have not been able to satisfy 

 myself. About this period, however, I have sometimes seen bodies, apparently composed 

 of precisely the same material as Figs. 6. 7, 9, undergoing something so very like cleavage 

 (Plate XLII, Fig. 8) that I hesitate to state that this act is not one of the stages in the 

 development of the filaria. The figure given (No. 8) is very carefully sketched, and, 

 like all the others, accurately to scale. It will be noticed that one end is partially 

 hidden by some granular matter. This I was not able to press away from the prepa- 

 ration. Other preparations of a like kind were also more or less hidden by granular 

 matter, and in some cases (unassociated, however, with any indications of fission) the 

 parasite appeared to be covered with an encrustation. With regard to the process of 

 division suggested by the appearance of No. 8 I can offer no opinion ; it is quite 

 possible that it forms a part of the developmental changes undergone by some other 

 parasite, — such, for instance, as a gregarine. About the fourth day there will also be seen 

 short, thick bodies (very appropriately described Dr. Manson as " sausage-shaped "), 

 almost perfectly still (Fig. 10), with a faint indication of a mouth ; and, in some of them, 

 a faint line may be detected suggestive of a commencing intestinal canal ; the escape 

 of a few granules on slight pressure towards the other, usually thicker, end, suggests 

 the existence of an anal aperture. The chief difficulty which I have experienced in 

 following these changes is to account for the transition of form at Fig. 7 to that re- 

 presented in Fig. 10. They are all, up to this figure, sketched as magnified by 300. 



The larval forms at Fig. 10 now rapidly increase in size, and gradually acquire a 



more elongated outline, and between the fourth and fifth days they may be found pre- 



enting the form shown at Fig. 11. The last figure, it will be noticed, is magnified 100 



diameters only, and the length of the larvae, therefore, is almost three times that of 



those delineated at Fig. 10. They also manifest greater activity. 



The highest stage of development which has come under my notice is that figured 

 at 12 as seen magnified 100 diameters. The anterior and posterior portions of a simi- 

 lar one, magnified 300 diameters, are delineated at Fig. 13, This measured -^^ of an 

 inch in length, and its width towards the middle was ^^^ ; near the anterior and pos- 

 terior ends they measured ■^'^^' across. The dimensions of another specimen which I 

 measured were J^" in length by y^Vir' i^ width at the broadest part. Dr. Manson 

 mentions that he has on four occasions observed larger specimens than these. 



Notwithstanding their activity and apparently robust condition, they nevertheless 

 are extremely fragile, very slight pressure of the cover-glass being sufficient to crush 

 them. When examined in the unbroken condition it is only with difficulty that the 

 alimentary canal can be distinguished beyond the junction of the oesophagus with the 

 intestine, but when carefully ruptured (as in Fig. 12) the tube may be distinguished. 

 I have not been able to distinguish any other differentiated viscus in any of the 

 specimens which have come under my observation, and, certainly, nothing suggestive 

 of differentiation of sex. 



