76 PllESIDEXTIAL ADDRESS — SECTION D. 



chaete, named by him Leptospira ictcroides, and cultivated by him 

 from cases of yellow fever. The morphology of the tiny spiro- 

 chaete was described. The transmitter, Stcgomyia fasciata, has 

 long been known, owing to the devoted labours of Carroll, Lazar 

 and Agrarnonte; the causal organism is now known, and the 

 chain of evidence is complete. 



Spirocceta icterohccmorragicu, now known to be the agent of 

 infectious jaundice, is present not only in man but in rats and 

 mice, producing little ill-effects in the rodents. The spirochete is 

 present in the urine of the hosts, and from food or water con- 

 taminated with infected rodent and human urine, the organism 

 reaches man. 



EiCKETTsiA Bodies. 



Rickettsia bodies, belonging to the Chlamydozoa, are the 

 causal agents of both trench fever and typhus, both of which 

 are louse-borne diseases. 



Trench fever was a great source of trouble during the Great 

 War, the causative agent, until lately, being unknown. How- 

 ever, Eickettsia bodies have been found in lice fed on trench 

 fever patients, and, according to Ledingham (1920) these Rickett- 

 sia bodies are agglutinated by immune serum obtained from 

 animals immunised with the infective excrement of lice. On the 

 other hand, trench fever Rickettsia were not agglutinated by the 

 serum of animals immunised with the excrement of normal lice. 

 This provides strong evidence for incriminating the minute 

 Chlamydozoon, Rickettsia, as the agent of trench fever. It may 

 be mentioned that, according to Swift, the virus of trench fever 

 is present in the blood of the patient at some period of the illness, 

 is often present in the urine, and sometimes in the sputum of tbe 

 patient. It is also found in the excrement and bodies of practic- 

 ally all lice that have fed several times on trench fever patients, 

 and occurs in such lice after a period of five to ten days after the 

 infective feeds. 



Tn typhus fever, Ricl-ettsia prowazclii, which occurs in lice, 

 and in tlie malpighian cells of the skin of an infected person, is 

 the recognised causal agent. 



There is not space to deal fully either with the Chlamydozoa 

 or with the group of filter-passing bodies, some of which im- 

 doubtedly are associated with disease. The development of new 

 technique for dealing with these bodies is in progress, but much 

 work still needs to be done on these elusive organisms, sonie of 

 which are found in the sea and in the soil. Shelley's remarks 

 regarding " The Cloud " might, perhaps, be applied to tliom : 



" I am the daughter of earth and water, 

 And the nursling of the sky : 

 I pass through the pores of the ocean and shores, 

 I change, but I cannot die." 



Helminthologv. 



]\Iuch attention has been devoted to helminthology in recent 

 years, and a number of interesting life cycles have been eluci- 

 dated. Some of these mav now be considered. 



