Subsequently, other experiments on dogs and men established the fact that the embryos of A. duodenale can enter the skin, and that they do so as a first step towards reaching the intestine. From the subcutaneous

Fig. 179.—A. duodenale. a, Young larva; b, head.	Fig. 180.—A. duodenale, mature larva.
(Partly after Looss.)

tissue they enter the blood-vessels and lymphatics, and by this channel are passively transferred to the lungs. Here they leave the capillaries, enter the air vesicles, and thence along the bronchi