



EI4 THE NORTHERN MICROSCOPIST. 

coccus, a single egg and embryo of which resulting in a cyst as 
before, has the pitting arrangement of the last ; but instead of 
developing single heads, they become secondary cysts, and each 
recommences the pitting on its own account. In this case either 
developing heads form the base of each, or forming into tertiary 
cysts, which ultimately have the same pitting arrangement and 
develop a tape-worm head from the base of each. ‘This process is. 
known as the formation of daughter and grand-daughter cysts, 
during which the primary one has been enlarging to an enormous 
extent, so much so that I have seen the lungs and livers of sheep 
and pigs almost entirely occupied by them; and on one occasion 
saw a human liver, of which very little remained except its outer 
envelope. I remember when a student, Dr. Cobbold relating to. 
us a case of a man in a London hospital, whose lungs and liver 
were so invaded by these cysts that there was communication® 
between the lungs, liver, and a suppurating wound in his side, so. 
that it was possible to have passed a bougie down the trachea, 
through the lungs, diaphraghm, and liver, and out again at the 
wound in the side. 
The period required for these changes to take place is as before 
remarked various ; some require only two months, whilst in that 
last referred to, a period of from one to two years is necessary 
for completion. After this, it is necessary that the cysticercus shall 
be transferred to the stomach of its ultimate host; and it is a 
noticeable provision of nature that the intermediary bearer is 
usually one, that in the ordinary course becomes a prey to the 
higher animal which is adapted to support the mature tape-worm. 
Thus cuttle fish bear a large number of cysticerci, which in the 
aduit condition infest the shark and allied fishes which prey upon 
them. The Zenia crassicollts of the cat resides in the cysticercal 
stage in the mouse. The Z: cucumerina of the dog passes 
through the Z7zchodectes latus (dog louse). Man becomes host to 
his particular cestode enemies by eating pork, beef, and mutton, 
which contain their larval forms. Rabbits and hares bear the 
Cysticercus pisiformis, which will only develop up in the dog, as 
the Z! serrata, and the facts arrived at by experiment with these 
particular worms may be briefly summed up thus :— 
First, feed a number of rabbits with eggs of Z: serrata, and kill 
the first rabbit. Twenty-four hours afterwards the blood will con- 
tain numerous six-hooked embryos, to be seen with a 1” objective. 
About fourth day kill another, and a number of specks may be 
found with a lens on examining the liver ; under the microscope 
they prove to be vesicles of about <1,” diameter. 
Fifth day they are about #4”; sixth day =,” ; twenty-first day 
are elongated and about ;4,” in length ; at about twenty-fourth day 
the vesicles have coalesced, forming canals along which the larvee 



