NOTES ON SOME TROPICAL DISEASES 35 



importance of the observation quoted from Manson in Part I. of 

 this work, that amoebae are often absent from the fluid removed 

 by aspiration, and that they are only found later in the discharge 

 in the dressings after the abscess has been opened and drained : 

 * The size of the amoebae varied from 10 yu, to 40 /*, usually 24 ^ 

 to 30 /A. Their shape is generally circular, but sometimes oval. 

 By careful focussing the surface is seen to be markedly convex when 

 entire. . . . They are not flattened discs, but globular masses. 

 They are bounded by a well-defined capsule or ectosarc, which is 

 often seen to be doubly refractile ; this. gives them the well-defined 

 outline which renders them easily distinguishable (even under a low 

 power) from most other structures. The interior presents a granular 

 appearance, and in some of the smaller amoebae this granular 

 material occupies the whole of the space ; but some of the larger 

 ones show a well-marked nucleus, while others do not.' This 

 variability as to the presence or absence of a nucleus is important. 

 When the nucleus is absent, protozoa are commonly in what is 

 known as the chromidial condition i.e., the chromatin is diffused as 

 a fine dust throughout the protoplasm. Prowazek 1 has worked out 

 the details of this change from the nucleated to the non-nucleated 

 condition in another amoeba the Plasmodiophora brassier. By close 

 observation and experiments by feeding cats, Schaudinn 2 found that 

 the Amoeba coli of Losch is not the organism that invades the 

 tissues and causes this disease ; the organism which does so is the 

 pathogenic amoeba he has named Entamceba histolytica. In its 

 vegetative stage this protozoon is characterized by having a tough 

 ectoplasm and by the ill-defined character of its nucleus. Vegetative 

 increase is by binary fission and by budding. Cyst-formation occurs 

 when the patient is recovering and the faeces are becoming solid. 

 The parasite then enters into the chromidial state, and buds from 

 3 fj, to 7 /A in diameter project from its surface, and, becoming 



1 Prowazek, Arbeit, aus der Kaiserlich Gesundheitsanite, vol. xxii., p. 396, 1905. 



2 Schaudinn, ibid.^ vol. xix , p. 560, 1903. A good account of Schaudinn's paper 

 is given by E. J. McWeeney in a paper on ' Parasitic Protozoa ' in the Transactions 

 of the Epidemiological Society, 1904-1905, vol. xxiv., new series. 



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