1919] VETERINARY MEDICINE. 285 



Recent discoveries concerning the life history of Ascaris lumbricoides, 

 B. H. Ransom and W. D. Foster {Jour. Pard.sitolornj, 5 {1919), No. 3, pp. 

 93-99). — The authors here review the results of recent investigations of A. 

 lumbricoides, and report upon studies carried on in continuation of those pre- 

 viously noted (E. S. R., 38, p. 385). 



The authors have found that in guinea pigs and rabbits the larvae behave 

 in respect to their development, migration, and elimination as they do in rats 

 and mice, and in respect to the fact that they are liable to cause a more or less 

 serious pneumonia. They have come to the conclusion that tbe real explanation 

 of the beluivior of Ascaris larva; in rats and mice is that the worms are merely 

 going through the same course as they do in their usual hosts, man and pig. 

 TIio only essential difference is that in unsuitable hosts, such as rats and mice, 

 the parasites are unable to complete their development to maturity, whereas, in 

 lumian being and pigs, after their migration through the lungs and return to 

 the alimentary tract they can continue their growth to the adult stage. 



The fact that immature worms that had develoi)ed beyond any stage yet ob- 

 tained from rats, mice, guinea pigs, or rabbits were recovered from a young 

 goat and a lamb after having fed them eggs of the pig Ascaris and other experi- 

 ments lend support to the common belief that A. ovis occasionally found in sheep 

 is merely the pig Ascaris in a strange host. " In a scale of host adaptations 

 we may, therefore, recognize three grades — rats, mice, guinea pigs, and rabbits 

 in the lowest, sheep and goats in the intermediate grade, and pigs in the high- 

 est, with which we may also include human beings, if it be true that the Ascaris 

 of man and of the pig are identical. . . . 



" The symptoms shown by experimentally infected pigs at the time of the 

 invasion of the lungs by the larvae are frequently exactly similar to those 

 exhibited by pigs suffering from so-called ' thumps,' a popular name for a serious 

 condition of very common occurrence among pigs, and it is accordingly not 

 improbable that Ascaris is an important factor in the production of ' thumps,' 

 especially when it is considered how very commonly Ascaris occurs as a parasite 

 of pigs." 



The factors which bring about the hatching of the eggs have not yet been 

 determined, the authors having been unable to cause more than a very small 

 percentage of the eggs to hatch outside the body in vitro. 



A list of 17 references to the literature is appended. 



Recent experiments on the life history of Ascaris lumbricoides, F. H. 

 Stewart {Brit. Merl. Jour., No. 3030 {1919), p. 102).— The author first refers 

 to the report of Ransom and Foster, previously noted (E. S. R., 38, p. 38.5), 

 after which he reports several experiments with young pigs in continuation 

 of the work previously noted (E. S. R., 39, p. .587). 



Doses of 22,000 ripe eggs of A. snilla each administered to two 4-day-old 

 pigs (A and B) and a dose of about .50,000 eggs to a pig (O), 2 months and 

 10 days old, resulted in the two former suffering from Ascaris pneumonia on 

 the eighth day after infection, while the latter, or older pig, showed no sign 

 of pulmonary trouble. • 



" Pig A was killed on the fourteenth day, and young forms of Ascaris meas- 

 uring between 2.5 and 3.8 mm. [0.1 to 0.15 in.] were found in great numbers 

 in the small intestine and cecum. Their heads had lost the appearance of 

 the larval head and had taken on the adult head character. Pig B was 

 killed on the nineteenth day, and although there can be no doubt that on the 

 eighth day the lungs contained thousands of active larvse, not a single worm 

 was found in the stomach, small intestine, cecum, or colon. The nature of the 

 feces found in the colon proved that the pig was not suffering from diarrhea 

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