l86 THE ANIMAL PARASITES OF MAN 



somum japonicum inhabits the arteries, the absence of integumental 

 protuberances might be easily explained by the fact that the 

 arterial current would maintain it in its proper position. 



In Catto's case the ova of the parasite were found chiefly in the 

 intestinal tract and its appendages. In the intestine, from caecum 

 to anus, the ova occupied roughly two concentric layers, the one 

 subperitoneal, where the ova were comparatively scarce, the other 

 in the submucous coat, where they were innumerable. Between 

 these zones in the muscular layers there were single or double rows 

 of eggs lying with their long axes at right angles to the bowel. In 

 the mucosa they were also plentiful, especially in the necrotic areas. 

 Of the intestinal tract, the rectum and appendix were most affected. 

 Everywhere throughout the small intestine ova were found, but only 

 in patches and in relatively small numbers. In the liver the ova 

 were plentiful, lying singly or in clusters embedded in the markedly 

 hypertrophied fibrous connective tissue. They were also found in 

 many of the enlarged mesenteric lymphatic glands, in the outer wall 

 of the gall-bladder, in the pancreas, in the liver capsule, and in the 

 fibrous coat of the larger mesenteric vessels. The eggs were not in 

 the capillaries which they are too large to enter but in the peri- 

 vascular tissue. Probably the female schist osoma has a means of 

 extruding them through the walls of the blood-vessel. Their further 

 distribution is probably due to the lymph stream. Where ova accu- 

 mulate they provoke a small-celled infiltration, which gives place 

 later to a. great proliferation of fibrous tissue. 



Nothing is known of the life history of this schistosoma. The 

 ova contain a ciliated embryo, which may develop in the faeces even 

 before they are evacuated. The geographical distribution of Schisto- 

 somum japonicum is probably a wide one, and Dr. Catto suggests 

 that the parasite was not recognised before because its ova in the 

 stools were mistaken for the ova of Uncinaria duodenalis, which 

 they resemble in size, shape and general appearance. [L. W. S.] 



Class II. Cestodes, Rud., 1808. 



Tapeworms have been known from ancient times at all events, the 

 large species inhabiting the intestines of man and there has never been 

 a doubt as to their animal nature. The large cysticerci of the domestic 

 animals (occasionally of man also) have been known for an equally 

 long period, but they were generally regarded as excrescences, or 

 hydatids, until almost simultaneously Redi in Italy, and Hartmann 

 and Wepfer in Germany, concluded from their movements and organisation 

 that they were of animal nature. From that time the cysticerci have 



