Page:Tropical Diseases.djvu/828

772 suddenly recover themselves with a jerk, and turn quickly on to their edges and begin swimming about again. This series of movements is constantly repeated.

The larva of D. medinensismeasures about 15 to 25 mm. in length by 0·50 to 0·75 mm. at its greatest breadth. The head is somewhat tapered and then abruptly rounded off. The tail is long, slender, but not quite sharply pointed. The alimentary canal can be readily detected. Towards the root of the tail two peculiar gland-like organs, placed opposite to each other,



can be made out. The cuticle is very distinctly transversely striated.

In clean water the larva remains alive for six days; in muddy water, or in moist earth, it will live from two to three weeks. If slowly desiccated it does not die; it may be resuscitated by placing it again in a little water.

Intermediary host.—If, by way of experiment, we place some dracunculus larvæ along with Cyclops quadricornis in a watch-glass we shall find that, after a few hours, the larvæ have transferred themselves to the interior of the body cavity of the cyclops, where they can be seen moving about, coiling and uncoiling themselves, with considerable activity (Fig. 152).