188 AMCEBA COLI. 



Their formation, as compared with the changes of a blood corpuscle, 

 is characterised by great rapidity, for they are sometimes protruded' 

 and retracted four or five times in a minute. They arise, indeed, so 

 suddenly as to produce the impression that the protoplasm flows out 

 at a circumscribed portion, forming a little drop of mucus. The 

 animals generally keep to one place during these movements, but 

 sometimes they creep slowly about, first sending out a long trans- 

 parent thread, then allowing the granular protoplasm to flow into this, 

 and, lastly, drawing the rest of the body forwards. These changes of 

 position take place comparatively slowly, the animals hardly advancing 

 the length of their body in a minute." 



The nucleus presents a globular, transparent, colourless, or faintly 

 yellow appearance, and varies in diameter from 0'0048 to 0'0069 mm. 

 It has but slight consistency, often changing its shape somewhat with 

 the movements of the parasite, and becoming sometimes more oval 

 or somewhat lengthened out, but regaining its original form on the 

 withdrawal of the pressure. In quiescent specimens it lies more in 

 the centre of the granular protoplasm, and is therefore observed only 

 with difficulty ; in actively moving forms it may occupy any position 

 throughout the body, and often lies near the surface of the body. In 

 the interior one may distinguish a nucleolus of very varied size and 

 refractive power. In individual cases its diameter is half that of 

 the nucleus. It is transparent, but in the smaller specimens shows 

 a dark contour, and has such power of refracting light that it some- 

 times looks not unlike a fat granule. The vacuoles in the protoplasm 

 are also of very varied size. Most of them are larger than the nucleus, 

 but some are only half as large ; exceptionally, one sometimes finds 

 them half as big as the whole animal. Their number varies from one 

 or two to six or eight, or even more, but the smaller numbers more 

 frequentty occur. In exceptional cases they seem to be wholly 

 absent, and only appear after the addition of water. After prolonged 

 observation, a distinct change of form is sometimes to be observed. 

 They sometimes become rather smaller, sometimes larger, and, as the 

 Amceba moves, may assume an oval or long bean-shaped, or even 

 irregular form. Distinct pulsations cannot, however, be observed. 



Besides the component parts, various foreign substances are some- 

 times found embedded in the protoplasm, especially Bacteria, Vibriones, 

 Micrococci, and chains of Mycothrix ; and exceptionally larger bodies, 

 such as red and white blood corpuscles, nuclei of detached cells, starch 

 grains, and other substances found in the intestine. After the ap- 

 plication of an enema of vermilion, given to the patient to test the 

 ingestive power of the Aincebm, particles of the pigment were to be 



seen in their interior. _,- ■*■ ^ i, hji- a^ 



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