88 THOMAS L. BANCROFT. 
being left but the enlarged nucleus, this then becomes fainter and 
fainter until it has disappeared. Extravasation of blood occurs 
along the tracks of some of the worms. Pieces of the worm are 
seen throughout the liver substance, apparently not following any 
particular vessels, although the great mass of eggs seem to be 
deposited in the portal canals, frequently in the hepatic artery. 
During the invasion of the worms the liver is in a state of acute 
atrophy, but after they have deposited their eggs, died, and been 
absorbed, which takes two or three weeks, the organ rapidly recovers 
itself, and but for the resultant cirrhosis, presents a normal appear- 
ance. Fibrinous pericarditis was present in those that were 
seriously affected by the parasite, and probably accounts for the 
dyspnoea, which is so marked a feature. 
The eggs die and become calcareous if a long interval elapse 
between infection and the rat’s death. One rat was examined six 
months after having been fed with a small number of mature eggs, 
and many of the eggs in its liver were found in a calcareous state. 
The eggs having been deposited in the liver remain there until 
the death of the rat; they never seem to occasion abscesses, nor 
pass to the intestine by the bile duct. Eggs in water placed in 
the sun die, and their protoplasm contracts to a ball. No experi- 
ments have yet been made to try if maturity can be hastened by 
recourse to the incubator. 
To ascertain how soon the eggs mature in water in the shade, 
the following experiment was made :—On July 13, 1892, some 
eggs were put into water, and on September 1, they were examined 
but no apparent change had occurred :—on October 11 they were 
again examined, the protoplasm was noticed to be altered slightly, 
in some it appeared to have divided into four :—on November 24 
the alteration was more pronounced, and in many faint traces of 
the embryo worms could be seen :—on December 12, perfect worms 
were visible. In five months therefore the worms appear, still 
they are even then not mature, for great pressure is required to 
cause their extrusion from the shells. 
