14 BULLETIN 817, U. S. DEPT. OF AGRICULTURE. 



during the first day or two after the eggs are swallowed, the larvae 

 that have migrated through the lungs begin to pass out of the body 

 in the feces about 9 days after infection and have usually all or prac- 

 tically all been eliminated in less than 3 weeks after infection. Dur- 

 ing their stay in the body they may increase in size from an origi- 

 nal length of 0.2 to 0.3 mm. to a length of nearly 2.5 mm. (Stewart), 

 most of them, however, reaching a length not exceeding 1.75 mm., and 

 some being not more than 1 mm. long when eliminated in the feces. 



Stewart (1916a) remarked upon the occurrence of larvse in the 

 spleen. We have occasionally observed larvse in the spleen, 2 being 

 present in the spleen of a mouse examined 23 days after infection, 8 

 in the spleen of a mouse examined 19 days after infection, and 1 in 

 the spleen of a mouse examined 9 days after infection — in this case 

 measuring 0.36 mm. in length. As a rule, however, the spleens of our 

 experimental animals, which were commonly but not always ex- 

 amined, showed no larvse, so that this organ may be considered an 

 unusual location. In one case a larva was found in the thyroid gland 

 of a mouse 23 days after infection. In another mouse 13 days after 

 infection larvse were found under the peritoneum in various places 

 in the abdominal cavity, including the Fallopian tubes. Probably the 

 larvse occur rather infrequently in the spleen, thyroid, and under the 

 peritoneum of the abdominal cavity, but in our examinations, except 

 in the case of the spleen, we rarely looked for them, in these places. 

 The kidneys have been examined repeatedly, but no larvse have been 

 found in them. 



It has been suggested that the larvse migrating from the intestine 

 reach the liver by way of the portal vein, continue to the heart in the 

 hepatic veins and vena cava, and from the heart to the lung in the 

 pulmonary artery, and it is possible that most of the larvse follow 

 this course. Evidently, however, in view of their occurrence in the 

 spleen, thyroid, etc., some of the larvse at least may migrate along 

 other paths. How they get to the spleen, thyroid, and under the 

 peritoneal lining of the abdominal cavity has not been explained. 

 The possibility is not excluded that in their migrations from the in- 

 testine some of the newly hatched larvse are carried in the lymphatics 

 more or less directly to the heart and reach the lungs without passing 

 through the liver. Perhaps some of these larvse, together with others 

 that pass very rapidly through the liver and are soon carried in the 

 portal circulation to the heart and lungs before they have increased 

 much in size, get into the pulmonary veins, notwithstanding the 

 intervening capillaries, are returned to the heart, and are then dis- 

 tributed to various parts of the body. 



Since the foregoing was written more than a year ago, two papers 

 by Yoshida (1919) have come to hand. In the latter of these papers 

 Yoshida gives the results of experiments from which he concludes 



