DIAGNOSIS 



1833 



The diagnosis of latent cases and of carriers is based on the finding 

 of the characteristic histol3rtica cysts containing four nuclei. It is 

 important to note that cysts are not often seen during the acute 

 attacks with blood and muco-pus. 



In the search, for cysts, only a small quantity of material should be used 

 well diluted with saline. The addition of a little iodine solution is useful, as 

 it makes the nuclei more visible. Dead cysts are easily stained by eosin, 

 while live ones are not. 



Cysts of Loeschia histolytica have to be differentiated principally from cysts 

 of L. coli, Vahlkamfia nana, amoebae of Limax type, Chilomastix, Lamhlia, and 

 from the structures known as Blastocystis hominis. The characters of all 

 these cysts have been given in detail in Chapters XVII. and XVIII. For 

 diagnostic purposes it is sufficient to remember the following : — 



I. Cysts of L. histolytica in fresh preparations from stools mixed with salt 

 solution appear as spherical, greenish, very refractile bodies 10-14 microns 

 in diameter, containing four nuclei (at times two) and one or two highly 

 refractile homogeneous rods known as chromidial bodies. Several vacuoles 

 may be present. Dobell and others have called attention to the fact that the 

 size may vary a great deal, there being races of histolytica [minuta type) 

 giving rise to much smaller cysts, 7 to 9 microns, and others to much larger 

 ones, 12 to 20 microns. 



II. Cysts of L. coli vary between 1 5 and 20 microns, are rarely larger, occasion- 

 ally smaller. They are clear spherical bodies of sharp outline, less refractile 

 than those of L. histolytica. They contain 8 nuclei, which appear as faint 

 granular rings with a central dot (karyosome). Often only one vacuole. 



III. Cysts of Vahlkamfia nana are oval or spherical structures 7 to 9 microns 

 in diameter, with one, two, or four nuclei, very rarely eight; in addition, a 

 variable number of highly refringent granules and sometimes a large dull 

 inclusion (glycogen). There is absence of chromidial bodies, and this dis- 

 tinguishes the cyst at once from the small ones of L. histolytica. 



IV. Cysts of amoebae of Limax type are found in stale stools, are always 

 small, uninucleated, and often have a thick wall of brownish colour. 



V. Cysts of Chilomastix mesnili are often lemon-shaped, and are charac- 

 terized by the presence of the chromatic rod (parabasal). 



VI. Cysts of Giardia intestinalis are easily recognized by their egg-shaped 

 appearance; they are about 14 microns in length and very transparent, so 

 that the lamblia can be seen within it with the characteristic central paired 

 rod-like structure in which originate the four pairs of fiagelli. 



VII. Cysts of Oicomonas, Bodo, Pvowazekia are very small, spherical, 

 6-8 microns in diameter, uninucleated, very similar to those of Amceha limax, 

 but the wall is not so thick nor of brownish colour, and the outline is more 

 regular. Sometimes, however, it is impossible to distinguish these cysts from 

 those of Amosha limax. They can always be differentiated, however, from 

 those of L. histolytica, as they are very small and uninucleated. 



VIII. The structures known as Blastocystis hominis — considered by some 

 authors to be vegetal organisms — are more or less spherical, 5 to 15 microns 

 in diameter, with a more delicate capsule than the cysts of Loeschise, and 

 contain a very large vacuole, which reduces the cytoplasm to a narrow rim 

 at one pole or both poles of the cyst. 



IX. Iodine cysts (I-cysts), These structures, described by Wenyon and 

 O'Connor, are generally roundish or oval, varying between 6 and 16 microns 

 in diameter, and show frequently a iodophilic body, which tends to be 

 rounded or lobed. 



To facilitate the detection of cysts when these are in very small 

 numbers various methods have been suggested, though in practice, 

 as shown by Miss Porter, such methods take a great deal of time, and 

 the results are not much better than those obtained by the simple 

 immediate microscopical examination of several preparations. It 



