Page:Tropical Diseases.djvu/816

760 organs. In a second necropsy, besides the ova in the liver, intestinal wall, and mesenteric glands, he found in a branch of the portal vein a parasite which he regarded as S. hæmatobium. In November, 1904, Catto discovered the same parasite in sections of the mesocolon from a Chinaman of the province of Fukien who died of cholera at St. John's Island Quarantine Station, Singapore. Later, Katsurada succeeded in communicating the parasite to cats by immersing their legs in the water of certain ponds and streams reported to convey the disease; and finally, in 1913, Miyairi and Suzuki traced the parasite, through a snail common in the infected districts, back to the vertebrate host.

The parasite (Fig. 141).—Schistosomum japonicum closely resembles in general structure S. hæmatobium. As in the latter, the suckers are placed close together at the anterior extremity of the body, the acetabulum or posterior sucker being distinctly pedunculated and funnel-shaped. The suckers in both sexes and the ventral surface of the body in the male are provided with minute spines. The distinctive characters of the new trematode are its smaller dimensions (male, 9 to 12 mm. in length by 0.5 mm. in breadth; female, 12 mm. in length by 0.4 mm. in breadth), and the larger size of the acetabulum as compared to the oral sucker. In the male the integument is smooth and non-tuberculated, and the posterior part of the body in the male is relatively wider, the sides overlapping one another far more extensively than in S. hæmatobium. Finally, the ova (70 to 75 μ. in length, 45 to 55 μ. in breadth) are smooth and possess no spine; but they possess, as Leiper has pointed out, what may pass as a rudimentary lateral spine in the form of a very minute and easily overlooked papilla—like an excrescence, in a cup-like depression in the shell. (Fig. 142.) A comparative study of the anatomy of the two schistosomidæ will probably show other morphological differences. Catto mentions a larger vas deferens and lobular testicles in the male, and a different