62 THE AMOEBAE LIVING IN MAN 



which I can find for these and similar statements is, however, that given 

 by Kuenen and Sweliengrebel : and it appears to be contained in their 

 statement that they have seen amoeboid forms of £. histolytica con- 

 taining bacteria and other foreign bodies. 



The explanation of this is very simple. In my experience £. histo- 

 lytica, in a freshly passed stool, does not as a rule contain bacteria in 

 its cytoplasm. This is true of all amoebae, whether large tissue-forms 

 containing red corpuscles, or precystic individuals. The latter are, 

 indeed, especially characterized by the absence of all ingested bodies 

 from their cytoplasm. They are the forms which, far from ingesting 

 solid bodies of any sort, have got rid of any inclusions which they may 

 previously have contained (red corpuscles, fragments of tissue cells, 

 etc.) in preparation for their encystation. They digest or egest food 

 particles, and never ingest them. In this respect they resemble the 

 encysting forms of E. ranarnm and every other amoeba — both parasitic 

 and free-living — with which I am acquainted. That bacteria are 

 generally absent from these amoebae in a freshly passed stool is, I think, 

 an indisputable fact. It is, however, equally true that bacteria can usually 

 be found in E. histolytica amoebae, of every sort, in stools which are not 

 fresh. In stale stools, or liver abscess pus, the majority of the amoebae 

 often contain bacteria ; and as a rule the staler the material, and the 

 more degenerate the amoebae in it, the more plentiful are the bacteria 

 contained in them. A similar observation can be made on the amoebae 

 in the tissues. In sections of ulcerated human intestines, which are very 

 rarely obtainable immediately after death, most or all of the amoebae 

 are usually degenerate : and many of them, as a rule, contain bacteria 

 in greater or less numbers. If a cat with acute amoebic dysentery is 

 killed, and its intestine fixed immediately by a good cytological method, 

 and then sectioned, as a rule not a single amoeba will be found to 

 contain bacteria. Although these are abundant in the gut contents 

 and the older necrotic tissues, the areas occupied by the amoebae, no 

 less than the amoebae themselves, are remarkably free from bacteria of 

 every sort. If, however, the infected cat is allowed to lie dead for some 

 time before its tissues are fixed, then the amoebae in the ulcers will 

 often be found subsequently to contain bacteria. In such circumstances 

 the amoebae are always more or less degenerate, and all more or less 

 full of bacteria — exactly as they are in human tissues obtained post 

 mortem. 



Examination of really fresh material will convince anybody, I think, 

 that £. histolytica, when in the amoeboid state, normally never contains 

 bacteria. Since these only appear in the amoebae when they are 

 degenerating or dead, the most reasonable way to account for this is, 

 obviously, to infer that dead and dying amoebae are subject to bacterial 

 invasion. Cells and dead protoplasm of all sorts, when present in the 

 gut contents, are readily invaded by bacteria ; and there is no obvious 

 reason why amoebae should not share the same fate. I have not the 

 slightest doubt that this is usually the correct explanation of the fact 

 that E. histolytica amoebae sometimes, and in certain circumstances, 

 contain bacteria. 



When individuals of E. histolytica are found to contain bacteria, then 

 careful examination always shows that the amoebae are degenerate. 

 Precystic amoebae, for example, containing numerous bacteria, are very 

 common in stools which are not perfectly fresh ; but as a rule every such 



