A Comparative Study of Cytoplasmic Inclusions (Volutin Granules) in Different Species of Trypanosomes

The literature of ‘volutin’ granules is reviewed in an attempt to clarify the meaning of the term in respect to trypanosomes. Fifteen species of trypanosomes have been examined by phase-contrast microscopy and the morphology and natural history of their cytoplasmic inclusions described. It is suggested that the formation of inclusions in trypanosomes circulating in the blood of mammals represents a constant phenomenon which is closely related in time to the immune reaction of the host; other evidence suggests that this relationship is not fortuitous. In addition, the formation of inclusions in Trypanosoma rhodesiense and T. lewisi appears to be related to polymorphism, notwithstanding the wide differences in the manner and time in which polymorphism (and associated cytoplasmic inclusions) occur within their cycles in the vertebrate host.