44 TROPICAL MEDICINE AND HYGIENE 



lateral spine ; these eggs are never passed through the 

 walls of the urinary tract, and are usually passed suffi- 

 ciently high up in the intestine to be intimately mixed 

 with the faeces. This hypothetical worm Sambon names. 

 Schistosomum mansoni. 



Schistosomum japonicurn is somewhat smaller than 

 S. hcematobium. The males are 10-5 mm. in length and 

 0-53 mm. in breadth, and the females 12 mm. in length and 

 0*4 mm. in thickness. The acetabulum is relatively larger, 

 and the dorsal surface of the male is smooth and not 

 tuberculated or spinous as in S. hcematobiinn. (Fig. 20.) 



S. japonicitm is found in the blood-vessels of the portal 

 system, and especially in the mesenteric vessels. The 

 eggs are found in the liver, lymphatic glands, and intes- 

 tinal submucosa, and in these situations may be found 

 in enormous numbers. In the submucosa of the vermi- 

 form appendix they may be numerous, and cause much 

 thickening. They have no spine, but there is a lateral 

 thickening surmounted by a small knob which probably 

 represents the spine, and are discharged by the intestine 

 in the faeces, and when passed the eggs contain the 

 miracidium, or developed embryo. 



The worm is common in some districts of Japan, and 

 occurs in China. It has been found in Chinese in the 

 Straits Settlements, and in the Philippines, but is probably 

 not indigenous in those countries. 



It is a common parasite of cats in Japan, and was first 

 described by Katsurada in Japan, and independently by 

 Catto in Singapore, in 1904. 



Little is known of the life-history or intermediate host, if 

 any, of the parasite. In- man, as the eggs are passed in the 

 faeces they must escape by the intestine or the bile-ducts. 

 What becomes of those in the lymphatic glands is 

 unknown. Wherever the eggs are deposited they set 

 up considerable tissue change with formation of masses 

 of embryonic fibrous tissue. In the intestines this 

 shows itself as thickening of the walls. In the liver, pale 

 fibrous patches are formed, and the lymphatic glands are 

 much enlarged and dense and fibrous. There is no pus 



