4 io POPULAR SCIENCE MONTHLY 



on rather to less familiar problems that are to-day puzzling the medical 

 world. 



Amoebic Dysentery 



Since 1860 various forms of Amoeba have been found in the human 

 intestine. In 1876 Loesch first claimed these rhizopods to be the cause 

 of dysentery, and since that time students of the subject have been 

 about equally divided into supporters of Loesch and his opponents. 

 In recent times, however, the belief is widespread that two forms of the 

 disease occur, one of which, tropical, pernicious, or amoebic dysentery, 

 is invariably accompanied by the rhizopod Entamoeba histolytica, 

 which Schaudinn distinguishes from the ordinary harmless intestinal 

 amoeba A. coll. This form becomes a tissue and cell-infecting 

 parasite and to this characteristic it owes its malignancy. Mus- 

 grave in the government laboratory at Manila has worked out the 

 organism most carefully and has been successful in producing the 

 disease in monkeys and other animals through cultures free from the 

 ordinary forms of bacteria. The life history of the Amoeba has been 

 followed by Schaudinn, and in the present place this is perhaps more 

 interesting than the pathological details. 



The Amoeba has little structural detail, a nucleated cell with minute 

 form changes, a slight differentiation into ectoplasm and entoplasm, a 

 great power of reproduction, by division and by budding, leading to 

 masses of the organisms in the intestine and attached organs, where 

 intestinal lesions, liver abscesses and the like, become the characteristic 

 features of the disease. One interesting phenomenon worked out by 

 Schaudinn is the preliminary nuclear metamorphosis before spore 

 formation. In the majority of rhizopods in which the life history is 

 known the formation of conjugating gametes is preceded by fragmenta- 

 tion of the nucleus either by division, or by a kind of nuclear secretion 

 of chromatin. A condition of the cell, known as that of the ' dis- 

 tributed nucleus/ results from this fragmentation and each fragment 

 of chromatin becomes the nucleus of one of the gametes. Unfor- 

 tunately, Schaudinn gives no figures in his preliminary publication on 

 Entamoeba, but his description tallies exactly with analogous processes 

 in other rhizopods, notably in Arcella, Centropyxis, Difflugia and 

 others. 



In Entamoeba as in these free-living rhizopods the spore-like bodies 

 resulting from this distributed condition of the nucleus conjugate and 

 so bring about a renewal of vitality of the parasite, favorable to the in- 

 fection of new hosts. Musgrave has shown that these parasites may 

 live a free life in ordinary drinking water and that infection takes 

 place presumably in this way, and his observations indicate that 

 Entamoeba is a facultative rather than an obligatory parasite of man. 



