100 1)11. CHISHOLM ON THE MALIS DRACUNCULUS. 
Th e ova, then, of the dracunculi being deposited in the water 
they peculiarly affect, are there hatched at the appointed season. 
All oviparous insects, we know, deposit their ova when they have 
acquired their perfect state ; and these ova remain unhatched 
until the return of the season when the heat necessary for their 
evolution has been established. The dracunculi, there is reason 
to believe, deposit their ova about the middle of spring, in warm 
climates ; and they are evolved about the middle or end of 
autumn. During the intermediate time, the worms seem to cease 
to exist ; for it appears from the preceding histories, that they 
almost never appear from the middle of March to the middle of 
November. 
The embryo worms insinuate themselves through the inter- 
stices of the cuticle under the cutis, and there gradually extend 
themselves into their full growth ; and then, by the irritation of 
their motions in extricating themselves from confinement, they 
produce a very troublesome and sometimes a fatal disease. But 
in the great number of instances I have witnessed, and as far as 
was possible at the time investigated, the ova seem to have 
been received into the stomach with the water in which they are 
suspended. They pass with the nutriment into the intestinal 
canal, are taken up with the chyle by the lacteals, and conveyed 
into the thoracic duct, from whence they are poured, with the 
fluid in which they thus circulate, into the blood, and are finally 
deposited in the cellular membrane, or, more generally, in the 
interstices of the muscles, and here, as in their more natural 
nidus, occupy the same period of what may be called incuba- 
tion. The young dracunculi proceed through the stadia of their 
growth, as they would have done had they entered in the worm 
state through the skin. 
An obvious objection may be made to this speculation, viz.: if 
th e esss of the dracunculi are thus received into the human 
system, and are thus evolved in it, how does it happen, that, of 
so many received into the stomach, so small a number arrive at 
maturity ? The answer, I apprehend, is as obvious as the ob- 
jection : (he action of the gastric fluid — the imperviousness of the 
mouths of the lacteals to any but the smallest — the involution of 
many in the excrementitious part of the food — the acrimonious 
nature of the bile — all contribute to the destruction of myriads 
of the eggs, in the course of their progress. 
Another objection may be founded on the circumstance of the 
insect being generally or more frequently extracted from the 
lower extremities. This, however, is divested of much weight, 
when it is admitted that the insect in the embryo state often in- 
sinuates itself through the skin; and, secondly, when the struc- 
