46 PARASITES OF MAN 



of the disintegration and resolution of their delicate bodies into 

 mere sarcode-masses. Still more rapidly poisonous effects 

 were produced by the addition of a little sherry or alcohol. 

 In solutions where the amount of spirit did not exceed one part 

 of spirit, proof strength, to fifty parts of water the effect was 

 the same." 



The development of the larva is equally well accomplished in 

 distilled water, in well-water, and in brackish water. In pure 

 sea-water the process goes on less satisfactorily. It was found, 

 indeed, that the addition of slightly saline water to ciliated 

 embryos, which were on the point of expiring in fresh water, 

 had the effect of reviving them for a time. These facts have 

 an important practical bearing. 



I have thus shown that the escape of the embryo is by no 

 means the slow process that Bilharz has described. Almost 

 invariably the shell bursts by a longitudinal slit extending over 

 fully two thirds of its long diameter, the first point of rupture 

 being commonly situated midway between the spine and the 

 centre of the shell. In normal births, so to speak, the head of 

 the animalcule emerges first ; but occasionally the animal 

 escapes sideways, and I have even seen the embryo extricate 

 itself tail foremost. Not unfrequently it has a difficulty in 

 detaching itself from the shell, in which case the egg is whirled 

 round and round by the half -freed prisoner (fig. 15). The 

 lodgment of the spine, however, against any foreign substance 

 affords the necessary leverage for ensuring escape. 



The larva never displays its proper elongated, spindle-shaped, 

 or cylindro-conical figure, until some short time after its escape 

 from the shell ; and, as a consequence of this, its powers of 

 locomotion are less marked at first than they are subsequently. 

 At the time of extrusion the larvae are commonly more or less 

 hour-glass shaped (fig. 11) ; this particular form being some- 

 times retained for many minutes or even for an hour. Usually 

 the Iarv89 have a tendency to acquire their normal shape imme- 

 diately after quitting the shell ; the oval, pear-shaped, and 

 variously contracted forms gradually merging into the charac- 

 teristic cone-shaped animalcule (fig. 10). In their fully devel- 

 oped condition, they exhibit the most lively movements ; and to 

 witness several hundreds of them rushing about with unceasing 

 activity is a curious sight. The phenomenon, moreover, loses 

 none of its interest from the consideration that only a few hours, 

 or it may have been minutes, previously, these now actively 



