Date of this Version
The Ascaris lumbricoides [roundworm], in one phase or another, has attracted the attention of parasitologists for many years, and during the last decade this parasite has been studied by a large number of investigators. The recent observations have been, to a great extent, directed along one line, the study of its life history. These investigators have established two important points: (a) That the life history of Ascaris is more complex than was supposed, as it has been found that a vasculo-pulmonary circuit of the larvae is necessary before they settle down in the intestine, where they develop to the adult stage; (b) that this parasite may not produce its greatest damage while in the intestine of swine or man. It is capable of exerting a more harmful effect during the interval between hatching in the intestine and its return to the intestine to develop to the adult stage. During this period all organs of the body may be involved, especially the lungs and liver.
Other phases of the Ascaris problem, such as the probable identity of the human and pig Ascaris, the question of intrauterine infection, parasitic allergy, immunity, etc., have been investigated and discussed by a number of workers. The great interest of farmers and swine raisers in this parasite induced the writer to undertake certain investigations along the line mentioned above, the results of which are here reported.