II. 



A NOTE ON MATERIAL AND METHODS. 



I DO not propose to describe in detail all the methods which I have 

 used in studying the amoebae of man. It seems to me unnecessary to 

 do so, because no special or peculiar methods are required for such a 

 study. Any good cytological or protozoological methods of obser- 

 vation, fixation, staining, etc., may be used successfully : and since I 

 have tried most of them, it would be merely wearisome to enumerate 

 them all individually. I wish to say a few words here, however, upon 

 certain points which are of particular importance. 



First, I would note that it is impossible to obtain a correct know- 

 ledge of the amoebae living in man without studying an abundance 

 of material. The study of only a few infections, or of insufficient 

 material from many, is very apt to lead to error. Secondly, the material 

 must be as fresh as possible, as all the amoebae which live in human 

 beings degenerate and die rapidly outside the body. Most of the 

 mistakes which have been made with regard to the morphology and 

 life-histories of these organisms have been due to failure to take 

 these two elementary precautions : and it is tragic to note, in reading 

 the literature, the vast time and trouble that have been wasted in the 

 study of wholly inadequate quantities of material of the poorest quality. 

 Whatever mistakes I may have made myself have not been due, as a 

 rule, to any lack of material. For a study of the intestinal amoebae I 

 have had more than enough. During the last few years I have per- 

 sonally examined over 10,000 human stools of all sorts : I have also 

 had at my disposal nearly 150 kittens experimentally infected with 

 E. histolytica : and I have been able, through the kindness of many 

 friends, to examine a considerable amount of pathological material 

 from cases of amoebic dysentery and other diseases. The obtaining of 

 living amoebae in a really fresh and healthy condition suitable for 

 careful microscopic study — both alive and after treatment by good 

 cytological methods — has not been easy. But the difficulties encoun- 

 tered have mostly been overcome, and I now feel that I have had 

 sufficient experience to enable me to speak with some confidence about 

 the intestinal amoebae at least. My confidence concerning most of the 

 facts recorded in the following pages has been greatly strengthened 

 by the confirmatory observations of a large number of fellow-workers 

 and pupils. The majority of my own observations have, indeed, become 

 the common everyday knowledge — confirmed time after time in the 

 daily routine — of dozens of workers who have been engaged with me in 

 this field of work during the War. 



I would note here, however, as a word of warning to many who have 

 studied this subject only from the practical standpoint of diagnosis, that 



