ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 113 



some years, especially in relation to human disease, recommend that 

 after the administration of a saline cathartic, the examination should 

 be made from the fluid portion of the stools. They significantly point 

 ■out that the diagnosis of amoebae should never be made unless they are 

 in a motile state, for even with typical resting or encysted forms 

 mistakes may occur. The stock medium for cultures used by the authors 

 is composed of agar 20 p.c, sodium chloride 0'3-0'5 p.c, extract of 

 beef ^0 • 3-0 ' 5 p.c. The finished medium should have an alkalinity of 

 1 p.c. to phenolphthalein. This is obtained by starting with an initial 

 alkalinity of 1'5 p.c. 



The stock medium was varied by diminishing the amount of salt 

 and beef extract, or by the addition of a minute amount of peptone. 

 Attempts to obtain pure cultures were always negative or doubtful, and 

 the authors' results were obtained from symbiotic cultures of amceba3 and 

 bacteria. Pure bacterial cultures were employed, and much difference 

 was found in the adaptability of particular bacteria for the purpose in 

 view. The medium, made into plates in the usual way, was inoculated 

 with the bacterial culture by smearing a loopful in concentric circles on 

 the surface of the agar, and then depositing some of the amceba culture 

 in the middle of the innermost bacterial circle. In from 24 to 72 hours 

 the protozoa will have passed one or more rings, and from such locations 

 may be taken for transplantings. 



Transplantation of a single amceba is effected by the following in- 

 genious device. Examine the surface of the plate, and locate an isolated 

 amceba in the centre of the field of a low-power lens. Turn on a dry 

 high-power lens, and lower it until it touches the surface of the medium. 

 Raise quickly, and examine with low-power lens whether the amceba is 

 still present, or has been picked up by the high-power objective. If 

 it has been, rub the aca of the objective gently over that of a new 

 plate. In this way symbiotic cultures from a single amoeba may be 

 obtained. 



Amoebae show marked preference for certain kinds of bacteria, but 

 this selectiveness may be due possibly to environment. The authors 

 had most success with the colon group. 



Amoebae do not develop below the surface of solid media unless in 

 association with a liquefying organism, and then do not extend beyond 

 the liquefied area. The growth and spread of amoebae over the surface 

 of plate cultures is quite rapid, and they seem to follow the path of the 

 bacteria. In relation to their pathogenicity the authors do not attach 

 much importance to the size, which has been stated by various writers to 

 vary from 5 to 50 //.. The optimum temperature of the amoeba?, studied 

 by the authors and obtained from different sources, is room temperature. 

 Growth was much less luxuriant at incubator and ice-box temperatures. 



For staining; living; amoebae the authors recommend a dilute solution 

 of neutral red, which should be run under the cover glass. For staining 

 permanent preparations of amoebae from cultures they praise Wright's 

 modification of the Eomanowsky method, the technique being the same 

 as that for blood films. 



The authors also notice the following procedures : (1) Zorn's method 

 consists in mixing a few cubic centimetres of faeces with ?> or 4 volumes 

 of a solution consisting of 15 parts of 1 p.c. chromic acid and 3 parts of 



Feb. 15th, 1005 I 



