PRESIDEXTIAL ADDRESS SECTIOX D. 67 



Another feature of interest is the occurrence of multiple 

 factors in disease. Tlius, in coccidiosis of grouse, Fantham found 

 that, in some cases, there had been a secondary invasion of the 

 tissues by bacteria, the merozoites of Eimeria avium having acted 

 as inoculating needles for the bacteria. It is probable that there 

 are similar occurrences in other infections, and it is suggested 

 that while the migrations of Ascaris larvae through the abdomen 

 and lungs of man are in themselves injurious, they also aid in 

 disseminating such organisms as tubercle bacilli. That the toxins 

 of bacteria are of more pathological import than the bacteria 

 themselves is known, as in the potato disease due to Bacillus 

 twmefaciens. Some worms, as Ascaris, are also known to pro- 

 duce a toxin. Lj-sius are produced among other parasitic worms, 

 and aid them in their passage through the tissues of the hosts. 



While there is a fund of general information in regard to 

 parasites left untouched, time, unfortunately, does not permit 

 of their consideration, and attention may now be directed to cer- 

 tain recent researches in the domains of protozoology, lielmin- 

 thology and entomology, particularly the two former. 



Protozoology. 



Among the recent advances in Protozoology, the following 

 may be considered: — 



AMEBIASIS. 



In connection with the Sarcodina, discussion as to possible 

 different races of Entamoeba histolytica has arisen. Dobell and 

 Jepps stated that there were at least five different races of 

 Entamoeba histolytica distinguishable from each other as shown 

 by curves representing dimensions of the cysts. Recently 

 Eodenhuis* controverts this opinion. He considers that there are 

 different factors which may cause irregularity in the obliquity of 

 curves. Such are (a) faulty technique in the measurement of 

 cysts ; (b) Amoebae may encyst at different stages of growth, so 

 producing cysts of different dimensions ; (c) the conditions of life 

 ' of the amoebae are influenced by their environment, such as the 

 diet of the host and variations in the intestinal fauna and flora. 

 Also, it is not known for certain whether an amoebic strain 

 changes its dimensions if transmitted from a carrier to another 

 person. Some of Eodenhuis 's observations on a family of carriers 

 suggest that such a change may occur. Eodenhuis obtained 

 curves that convinced him of the existence simultaneously of 

 different races of Entamoeba histolytica in one patient. He even 

 considers that the small strains are a different Entamoeba and 

 names it E. tenuis, his final conclusion being that the exstence of 

 different races within the species E. histolytica lias not yet been 

 proved. 



TRYPAXOSOMIASIS. 



One of the needless controversies of relatively recent times 

 has centred round the identity or otherwise of Trypanosoma 



* Trop. Diseases Bulletin, xix, p. 331 



