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748 Lutz, in Brazil, has confirmed Leiper's discovery of the role of the genus Planorbis in regard to S. mansoni, the species in that country being P. olivaceus; and Becker in South Africa has similarly confirmed Leiper's work as regards S. hæmatobium, the efficient species being Physopsis africana, a mollusc closely allied to Bulinus.

Symptoms.—The symptoms produced by schistosomum vary in degree within very wide limits. In the vast majority of instances the patient experiences

no trouble whatever; in other instances the suffering is very great. Indirectly, from the serious nature of the lesions of the urinary organs to which it may give rise, schistosomum is an occasional cause of death.

The most characteristic symptom of its presence in the wall of the bladder is the passage of blood at the end of micturition, with or without a sense of urinary irritation. The quantity of blood passed and the degree of irritation are increased by exercise, by dietetic indiscretions, and by all such causes as are calculated to induce or aggravate cystitis. As a rule,