Doctors Lewert and Lee should be congratulated for the very fine and detailed work represented by their necessarily brief presentation. Their work illustrates the utility of a many-sided attack, particularly when any one line of evidence may not by itself be capable of giving definitive conclusions. It also illustrates how a study of skin penetrating mechanisms in helminths, imaginatively pursued can illuminate some of the mechanisms of age and acquired immunity.
Like all new work, it raises further questions. Thus, the histochemical approach as a tool in studying helminth infections is very rewarding, but it would also be of great interest to know which of the anatomical structures of the worms are responsible in this case for the enzyme production. We have been able to show this with the adults of the dog hookworm by dissecting out various structures and testing saline extracts of them for physiological activity.