PART II. CHARACTERS AND DIAGNOSIS 77 



of this kind was described by one of us (C. M. W.). A man had 

 repeated attacks of this kind during several years. It is difficult 

 to explain the presence of the large quantity of mucus on the 

 occasions of the attacks, and above all the crowding of the mucus 

 by the flagellates, without assuming that the mucus must be pro- 

 duced by the intestine at the site of the lamblia infection and that 

 the flagellates are directly responsible for its production. We thus 

 have much more proof of the pathogenicity of lamblia than in the 

 case of either trichomonas, tetramitus, or any of the rarer flagel- 

 lates, all of which are most usually encountered in diarrhceic 

 conditions in which mucus production is not generally a feature of 

 the case. 



(12) Tetramitus mesnili. Free and Encysted Forms. 

 (Plate II, figs. 6 to 18.) * 



This flagellate is of very common occurrence and has been more 

 frequently found since we have been able definitely to recognize the 

 encysted form which is at times the only stage met with in the stool. 



Now that it is being generally recognized, the flagellate will 

 undoubtedly prove to be of world-wide distribution. It has certainly 

 often been mistaken for trichomonas and possibly other organisms, 

 though attention to details of structure should prevent any such 

 errors in the future. One of us (C. M. W.) has noted tetramitus in 

 iron hsematoxylin-stained films of faeces from the Philippines and 

 Panama, two places from which the flagellate has not hitherto 

 been recorded. In these places the flagellate must have been seen 

 and described under other names. The flagellate is typically pear- 

 shaped, though very frequently it is somewhat flattened or even 

 leaf-like, while the long-drawn-out flattened posterior extremity may 

 be twisted and folded in a variety of ways to produce peculiar 

 grooves and spiral turns. The figures represent some of these 

 twisted forms which are so common that they can hardly be called 

 abnormal. (Plate II, figs. 6 to 9.) * 



It seems most probable that Tetramitus mesnili multiplies as 

 other intestinal flagellates by binary fission, but we have not yet met 

 with the dividing stages. 



We have, however, been able definitely to recognize the encysted 

 forms of this flagellate, and these are of importance because an 

 infection can be recognized by them just as a lamblia infection can 



* See inset between pages 148 and 149. 



