16 



appreciated, must be taken in conjunction with that done 

 previously. The cases examined by the Liverpool workers were 

 more numerous, and really form the backbone of the whole inquiry. 

 The newer findings here presented are supplementary, and the 

 two series must be added together in order that their significance 

 may have a maximal value. Moreover, since no comprehensive 

 treatment of this subject has previously been possible, and since, 

 in consequence, no complete survey of it has been attempted, 

 it has seemed to me opportune to summarize all the information 

 at present available. I have therefore extended the scope of the 

 present Report so as to include the following subjects — to each 

 of which a separate chapter will be devoted : 



1. The older records of the occurrence of intestinal protozoa in 

 the population of Britain. 



2. The recent reports on the same subject — comprising a sum- 

 mary of the results obtained by the Liverpool workers, and the 

 newer findings of the workers under the War Office Committee- 

 (now published here for the first time). 



3. A summary of all the results so far obtained, with a dis- 

 cussion of certain points of particular interest. 



4. A brief review of certain similar observations recently made 

 in France, Holland, and Germany. 



And in a final chapter I will present very briefly what seem 

 to me to be the most important conclusions deducible from the 

 facts recorded in all the antecedent chapters. 



Infections with intestinal protozoa are, in general, very per- 

 sistent ; and we know that they are by no means uncommon in 

 many foreign countries. Consequently, it has seemed to me 

 necessary, for present purposes, to investigate particularly the 

 intestinal protozoa of persons who have never been abroad. 

 When such persons are found to be infected, it can be said with 

 certainty that their infections were acquired in Britain. It may 

 be urged, however, that even in such cases the infection may not 

 be truly indigenous, but may have been acquired from some im- 

 ported foreign source — from a home-coming soldier, for example, 

 returning from a country where the infection is endemic. This 

 objection is, I think, negligible ; for even if the explanation were 

 true, it would not invalidate the conclusion that infection can be- 

 acquired in this country, and it would demonstrate, moreover,, 

 that the conditions here are suitable for such infections to spread 

 — a very important point. For if they can spread now, they 

 could have done so before, and with a fluctuating population like 

 ours there is every reason to suppose that the infection — whatever 

 it may be, and whenever it may have been first imported in the 

 past — would thus long ago have established itself and become- 

 as truly ' endemic ' as it was in its country of origin. 



As regards the present classification of records into ' old ' and 

 ' new ', I would only remark that it is purely arbitrary, and done- 

 for convenience. What we have seen occurring during the War 



