49 
(1) We know that uncinariasis is spread through the feces: we know 
further that when the embryos hatch from th(‘ thi'v haive the 
feces and enter the surrnundino- water or moist earth, while theiv is no 
satisfactoiy evidence to show that they are blown around in the air in a 
dry state. (See Stiles, llM):>b, p. 199.) Now, assume that a juu-son walks 
over infected oround; if that around is clay, 1 k‘ do(‘s not disturb the 
embryos which have crawled beneath the sui-face, exc(‘pt in wet places; 
if, on the other hand, the o-round is sand, he not oidy stirs it up while 
walking, thus bringino- the young wa)rms nearer the surface again and 
thereby increasing their chances of producing an infection, but he is 
also likely to carry away particles of sand, together with embryos, 
with him on his shoes or feet, thus increasing his chances of becoming 
infected. It is further clear that children playing in sand will stir up 
more embrvos than when playing on a clay soil, and will thus increase 
their chances of infection. 
(2) An additional explanation is that water will not pass through clay 
as it will through sand; hence on clay soil the embryos stand a gn*at(‘r 
chance of perishing or of being washed b}- rain into the streams. On 
sand, however, the embryos might perhaps work their way through 
the soil" with the water, and thus infect surface wells. In advancintr 
this hypothesis, I am not unmindful of the view, supported by excel- 
lent observers, that, since the embiTos sink in water, driidving water 
is not necessarily a common source of infection. Granted that they 
do sink in water, a water bucket in a well also sinks, and the water 
from surface wells frecpienth^ contains sand particles that are hc'avier 
and larger than UncinavLa larvie; hence we can not altogether ignore 
the drinking water. as a possible source of infection. If, on the other 
hand, drinking water were the only source of infection, it is probable 
that in families where uncinariasis exists the intensity of the di.sease 
would show a greater tendency to uniformity. 
Giles has (‘xamined 5<) specimens of water from wells and ponds of 
villao’es ati'ect(‘(l with hookworm di.seas(‘ and 1<I of tluvsi' he found bv 
chemical and microscopical examination to 1 h‘ ""bad" or ""^'erv bad." 
Yet on Old}' one occa.sion did he find a rhabdite of doubtful origin in 
water. (Sandwith, 1894, p. 9.) 
(8) Oxygen is necessary to the develoi)m(Mit of the embryos and 
larvie, and it does not seem unreasonal)le to assunu* that .sand would 
In an article winch has jnst api)carc‘(l, L<)f)ss (ia03, p. .‘{.‘{1 ) says: 
“ Further, during the six years of niy residence in Cairo [I'^ypt], I have not heanl, 
iij) to the present time, of a single case [of hookworm diseasi*] in an lairopran nny 
own cas(‘, of course, excepted). This fact speaks all the less [s(» much the less] in 
favor of the assumption (.>f a more common di.ssemination [i. t*., infection] of tin* 
disea.se through the drinkin<j; water, vegetables, etc., since [as] fhr mntun honkirunn 
larnv, as experiments have sJion'n, ]xu<s throiajh (he ordinaia/ sand fdtrr irith Murpnsnuj 
rapklitij, and this even irhm the irater is allowed, not to run off, hut to stand.''' [ltalii*s 
not in the original German.] 
19558— No. 10-08- 4 
