COMPARATIVE. STUDY. OF AMCEB^. 265 



Twenty-five samples of tap water from the Manila supply have been 

 examined microscopically, after enriching and incubating at room tem- 

 perature, and by cultures made on Musgrave and Clegg's medium. As 

 the study of the parasitic amoebae progressed it became apparent that 

 it was unnecessary to examine a larger number of samples, to con- 

 centrate the amoebic fauna by filtration of large quantities of the water, 

 or to study the amoebaj from other surface waters, as had been originally 

 intended. In 33 out of the 25 samples of water amoeba were found 

 microscopically and culturally. In addition to these 33 cultures of 

 amoebae, one culture isolated by Dr. A. W. Sellards in the Biological 

 Laboratory of the Bureau of Science, and one isolated by Dr. E. B. 

 Vedder at the Division Hospital of the United States Army from the 

 Manila water supply have been studied. 



Of these 35 cultures of amoebje, twenty-four have been found to be 

 of one and the same species (Plate I, figs. 1 and 3) ; one culture was 

 a distinct species (Plate I, fig. 3). Both species appear to belong to 

 the so-called Umax group of water amoebae, but because of the imperfect 

 descriptions I have not attempted to identify them with the names 

 in the literature, or to add to the confusion by giving them new names; 

 nor is it necessary; it is sufficient for our purpose to determine the 

 generic characters of these two species. This type of amoeboid organism 

 (figs. 1 to 3) is characterized by an amoeboid trophozoite in which the 

 nucleus is situated centrally in the resting organism and in which the 

 chromatin of the nucleus is collected into a relatively large and dense 

 Jjaryosome that is surrounded by an achromatic halo, which possesses with 

 rare exceptions, a contractile vacuole, and which reproduces by binary 

 fission and by spore-formation (Walker, 1908) ; by an encysted stage 

 that has a single nucleus of the same structure as that of the trophozoite, 

 and in which no reproduction takes place; and by multiplying and 

 encysting freely upon artificial culture media. These characters are 

 those of the genus Amala Erenberg of which Amceha protens Leidy is 

 the type species. 



AMCEB^ CULTIVABLE FROM THE INTESTINAL TRACT OP MAN. 



The material from which these cultures have been made has consisted 

 of fresh stools containing amoebae from 113 healthy persons or persons 

 suffering from diseases other than amoebic dysentery, and from 31 cases 

 of amoebic dysentery, and pus containing amoebae from 3 cases of amoebic 

 liver-abscess, obtained from the drainage tube after operation and, also, 

 in one of the cases, post-mortem from the infected liver. This material 

 has been obtained chiefly from the hospital of Bilibid Prison, but in 

 part from the different hospitals in Manila. I am indebted to the 

 physicians in charge of these hospitals and to several of my colleagues 



