* 
€ 
ee ee ee ee eee ee 
7 . 
27 
system is represented by one or two ganglia near the mouth, and 
‘cords proceeding down the body. The vascular system by con- 
tractile canals communicating with the mouth, and spreading over 
the body, but observers are not agreed about the distribution of 
the nervous cords and contractile canals. The reproductive 
powers of these worms are enormous, Dr. Kstricht calculating that 
a mature female ascaris may carry 64 millions of eggs. What 
becomes of this innumerable horde? Doubtless, many of them 
perish, perhaps devoured by birds, or other animals incapable of 
offering them suitable lodgings. But, of one thing we are certain, 
and that is, the tenacity with which they stick to life. Professor 
Owen mentions a nematoid worm exhibit vital movements after 
boiling for an hour in a codfish. Many instances are recorded of 
their resurrection after being dried ; and others, after being soaked 
in spirits of wine and turpentine. The eggs are ovoid and covered 
with a transparent envelope. Rechter placed some ova squeezed 
out of an ascaris into some water and watched them from time to 
time by the microscope. Segmentation having taken place, the 
developement of the young was complete in fourteen days. They 
moved with great briskness, but did not break through their shells. 
. This continued during the autumn, and during the winter they 
were in a quieter state of mind. Thus, it is probable they remain 
encysted for a considerable period, until chance throws them in 
favourable circumstances, when they break through their shells and 
commence life on their own account. Nothing, however, for 
certain, is known of their doings from the time they leave the 
parent till they turn up like base coin in the intestine of some 
animal, Probably they are about in great numbers swept along 
by the wind, alighting in stagnant pools, wandering about perhaps 
among the green pastures of Beddington, floating down the Wandle, 
or lurking in some gutter on the look out for a thirsty dog. It is 
_ evident there are a thousand chances to one that any single worm 
ever finds its way to a suitable abode, and but for their enormous 
powers of reproduction their race must become extinct. There are 
two factors necessary for their developement—the presence of the 
ova and a suitable soil on which they may flourish. They are 
more likely to flourish in that individual animal that is out of con- 
dition. One may often notice it is the sickly fruit tree on which 
the blight appears. Anyone who has kept dogs must have noticed 
if the dog gets at all out of condition, he soon swarms with fleas 
and other vermin. I have seen this in dogs kept for experiment, 
that when put upon certain diets for long together, as fat or starch, 
and when they have undergone operations and got out of condi- 
tion, they swarm with vermin. However, dogs are seldom wholly 
free from entozoa, from their irregular mode of getting a living; 
q - eating and drinking any refuse, they must constantly be exposed to 
_ their inroads. Out of twenty-five dogs I have examined there were 
