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scolex is pushed when the larval metamorphosis takes place—but not 
evaginated in the strict sense of the word. I have seen larvae with the 
scolex pushed out and still adherent to the “ post-cephalic segment ” but 
in two series of sections there is no trace of the opening. If we take 
a globular cyst and dissect it with needles first of all an outer covering 
comes away—this is partly larval but must also be made up in part of 
tissues from the host. Within this outer cyst is the larva proper. If 
one dissects the latter in the same manner an apparent outer capsule 
can be picked away, and within this is another vesicle containing the 
scolex. What we first dissect away is the post-cephalic part of the 
larva and the inner vesicle is the receptaculum. 
In some cases the scolex is relatively large, may be coiled up in 
a double S-shaped form, and may lie apparently quite freely within the 
receptaculum. I believe that this is the case in the older Plerocercoid 
larvae: that the opening of the receptaculum may close up completely; 
that the scolex may become separated from the other part of the larva; 
and may only be liberated when the double or treble cyst round it is 
digested within the alimentary canal of the final host. I have never 
seen any indication of beginning segmentation in the oldest of these 
Plerocercoid larvae. Obviously very many of the larvae must de¬ 
generate since not all their hosts have the evil fortune to be eaten by 
the final hosts. So one finds cysts which indicate that they are the 
degenerate remains of larvae only by the presence of the calcareous 
corpuscles, or by that of some waxy substance. 
The Oncosphere larvae, when liberated from the digested proglottis, 
probably pass through the wall of the stomach or intestine and enter 
the blood vessels. Usually the latter will be small factors of the 
hepatic portal system, so that the larvae must find their way through 
the liver and so into the systemic circulation, and in this way they will 
be carried to remote parts of the body of the host. One would 
conclude that a general infection must often take place; nevertheless, 
it is very rare and the reason may be that the larvae degenerate in 
the arterial blood stream: it may be that they are obligatory anaerobes. 
In the great majority of cases the infection is that of the peritoneum. 
The larvae in such cases have doubtless been carried into the arterioles 
of the peritoneum or mesenteries, and then they become arrested by 
the decreasing calibre of the arterial twigs in which they are circulating. 
They then begin to grow in size occluding the blood vessel, and pro¬ 
ducing a nodular svvelling on the course of the latter. If the vessel lies 
near to the surface in the peritoneum covering the stomach or intestine. 
