PRESIDENTIAL ADDRESS^SECTION D. 87 



preventive measures against ancylostomiasis and on more effective 

 treatment of it. The great activities of the Rockefeller Institute 

 in its hookworm campaign are well known and have extended to 

 practically every country where hookworms are present. The 

 reduction in tropical ana?mia as a result of this campaign has 

 been great, and better sanitation, aided by the intensive use of 

 thymol in infected areas, has largely conquered the malady. 



ASCARIASIS. 



Another source of ill to man and beast is the round worm, 

 Ascaris. The form infecting man is the large round worm, 

 Ascaris lumbricoides ; the pig-infesting form is A. suilla. Great 

 interest attaches to the larval development and mode of infection 

 of the host of these species. Most of the results have accrued 

 from the work of Stewart* (1916-18), which has been repeated 

 and confirmed by many workers in Europe, America and Japan. 

 Until recently it was believed that an invertebrate intermediate 

 host was necessary for Ascaris. Such is not the case, infection 

 occurring by direct ingestion of ova. Stewart found that ripe 

 ova gave better results in experimental animals than freshly shed 

 ones. He also determined that the larvae performed an extensive 

 migration in the body of the vertebrate host and did not pass 

 their whole life in the intestine. The larvae hatch from the ova 

 in the small intestine. They are fragile, but they bore their way 

 through the mucosa, and, by way of the blood stream, reach the 

 liver. From the liver they migrate to the lungs, where they 

 remain for about 8 days. They then pass into the trachea, and 

 on about the ninth day, some begin to migrate back to the 

 intestine, though others persist in the lungs for as much as 15 

 days. By the tenth day, migration is fully established, and the 

 larvae pass rapidly through the stomach and small intestine, to 

 establish themselves in the caecum and upper colon. The passage 

 of the larvae through the lungs is attended by bronchitic symp- 

 toms, and " verminous bronchitis " is due to Ascaris as well as 

 to other causes. Ascaris suilla, according to Stewart, undoubtedly 

 causes an Ascaris pneumonia in pigs. He also states that there 

 is " reason for supposing that a great deal of the debility of the 

 natives of the tropics is due to ascariasis, and that this disease 

 is at least equal to ancylostomiasis in economic importance." 

 Yoshida, working on ascariasis in Japan, found that the lungs of 

 infected animals show notable hiBmorrhages and frequently 

 pneumonic reactions, the severity being proportional to the degree 

 and duration of infestation. 



In South Africa, Ascaris hunhricoides is almost the com- 

 monest round worm of natives. Ascaris suilla occurs in a large 

 proportion of pigs and sometimes in man. The transference of 

 the ova of these parasites to man by way of dust contaminated 

 with infected faeces and by flies is undoubtedly a source of 

 danger, and has afforded an explanation of some bronchitic 

 symptoms in certain children, for which no adequate cause could 

 be assigned. 



* See Parasitology, ix, x. 



