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160 the break-up is only partial, a certain number of the more feeble and less mobile parasites remaining together and slowly dying. The significance of this phenomenon has yet to be ascertained. Some authors believe that it indicates a recuperative molecular interchange between the associates.

In cultures, in many instances, trypanosomes acquire a spherical form and undergo multiple division.

Fig. 44.—Agglutination of Trypanosoma lewisi in the defibrinated blood of an immunized rat. (After Laveran.)

They lose their flagella in the process, certain of the division forms subsequently acquiring such an organ, which now invariably springs, as already mentioned, directly from the blepharoplast. These culture forms possibly represent a stage in the life of the parasite which, in normal conditions, is passed in the vertebrate host, or, more probably, in the insect host.

How long a trypanosome infection may persist in the human body has not been definitely determined,