282 J.v.i /v'A'OA'/ON/N A.\i> /JxnorAhws/ris.u 



Another pro!)!*'!!! is tluit of the roh' pLnyed by the 

 aiia('rol)ic fund ions of .sonic intestinal worms in the de- 

 veh)])ni('nt of tlieir wandering habits wlien tliey invade 

 tile body of a host as hirvae. In the case of Ascaris, for 

 example, as is well known, the larvae, developed from 

 the eggs and set free within the small intestine, do not 

 settle down there at once, despite the fact that the small 

 intestine represents the normal habitat of the grown 

 worms. On the contrary, they bore into the intestinal 

 wall, penetrate into the blood vessels and are carried by 

 the blood stream to the lungs, via liver and heart. There 

 they break out from the blood vessels, penetrate into the 

 air passages and wander up the trachea to the throat; 

 they are then swallowed and, passing through the esoph- 

 agus and stomach, they finally again reach the small in- 

 testine whence they started. This circuit takes about 

 ten days and during this time the larvae grow consid- 

 erably. Pintner (1922) developed the idea that the bio- 

 logical reason underlying this curious phenomenon must 

 be sought in the fact that many intestinal worms survive 

 in their normal environment only because of their ability 

 to live anaerobically. But to live anaerobically they 

 require glycogen. The wanderings of the larvae would 

 be undertaken to permit the formation of a glycogen re- 

 serve; during their stay in the blood stream they have 

 access to so much oxygen that an aerobic metabolism 

 would be possible, and to so much sugar that a glycogen 

 synthesis can take place. 



This theory is ingenious, but does not seem to be back- 

 ed by the experimental evidence. Stepanow-Grigoriew 

 and Hoeppli (1926) pointed out that even old Ascaris 

 larvae (embryonated eggs stored for six months), con- 

 tain glycogen, and the same holds for young filariform 

 larvae of Strougijloides stercoralis. It is true that the 

 glycogen content of these nematode larvae increases dur- 

 ing their wanderings. (This was noticed both by Step- 



