30 
Fifth stage {vnth definite huccal capside ). — The worm is now about 
1.9 (male) to 2 mm. (female) long, 12 to 14 p in diameter — veiy much 
smaller than the adult forms. It is estimated that the parasites 
require about four to hve or six weeks from the time of infection to 
become mature. 
SOURCE OF INFECTION OF UNCINARIASIS. 
The worms may be swallowed in contaminated food or in drinking 
water during or after the second ecdysis. Persons handling dirt are 
especially apt to get the microscopic worms on their hands, and it is 
an easy matter to transfer them to the mouth, either directl}^ b}^ biting 
the linger nails or sucking the lingers, or indirectly with food. In 
prevention , therefore, careful personal habits and pure drinking water 
are indicated. 
Some writers state that the young stages are scattered in the air by 
the wind and in a dry state, the inference being that they may then 
be breathed in or may contaminate food. While not caring to go to 
the extreme of stating that such a method of dissemination or infection 
is impossible, my own observations on this class of parasites do not 
lead me to attach any importance to aerial infection. As a rule, 
drying-out results in a high mortality among nematode larvae, embryos, 
and eggs, while moisture, on the other hand, is necessary for their 
existence. Now, uncinariasis is not so common as to fill the air with 
dried larvae, and the chances of inhaling the latter appear to be almost 
infinitesimally small. Since the worms do not increase in number in 
the intestinal tract, we should therefore expect (in case aerial infection 
were common) to find rather few cases of severe infection, but a more 
or less uniform light infection of nearly all persons or animals inhabit- 
ing an infected area, since all are breathing the same air. Further, as 
adults breathe more air than children we should expect the former to 
present the cases of heaviest infection. We should also expect to find 
the disease more general in dry years than in wet seasons. Such, how- 
ever, does not appear to be the case. Cases of infection vary greatly 
in intensit}", and the losses from nematode diseases in sheep are much 
less in dry years and in diy localities than in wet seasons. As a 
matter of fact, few factors can be conceived of which would probably 
result in killing more germs of the disease than would dry winds. 
In preventing uncinariasis and nematode diseases in general among 
live stock, S3^stematic draining and burning of pastures are strongly 
advocated. 
Looss (1898, 1901) recentl^^ suggested that the larvae may enter the 
human body by way of the skin and then pass through the body to 
the intestine. Startling as this view is, Looss (see Sandwith, 1902) 
has recently demonstrated the correctness of it. (See p. 59.) 
