16 
The anatomical character which distiuofuishes the o^enus V neinaria 
is the dorsal curvature of tlie anterior extremity of the body, due to 
the shortness of the dorsal wall of the buccal capsule and resulting in 
bringing the mouth into a dorsal instead of a terminal or a ventral 
position. 
In many medical writings this genus is ivdmed Anc^ i/7osfoma , a word 
which is spelled in at least nine different ways, and the disease is 
spoken of as onchylodorniash. This nomenclature and terminology 
are due to the fact that when the hookworm {Vncinarla duodenal is) of 
man was first described, in 1ST3. it was supposed to represent a new 
genus {Agchylosfoma). As a matter of fact, however, it is generally 
acknowledged to be congeneric with a worm described in 1789 as 
Tdncmaria. By the international *Aaw of priority/' therefore, the 
names Agchylostoma, AnchyJostoma, etc., fall into .synonymy until it 
can be shown that the two species are not congeneric. (See p. Id.) 
In explanation to physicians it may be here stated that zoologists 
are obliged to deal with hundreds of thousands of technical names, 
and on this account they have been forced to adopt very rigid rules 
governing their use. Our most important rule is the "law of prior- 
ity." which to us is as essential as is the "code of ethics'’ to the 
physician. ’ 
The genus Uncina.ria contains blood-sucking wonns of the worst 
type. They are usually not over an inch in length nor thicker than 
an ordinary hatpin. They are provided with a heavy armature of 
sharp teeth, by means of which they pierce the intestinal mucosa of 
their host. They have also an unusually strong muscular esophagus, 
wliich serves as a pump during the act of sucking blood. An important 
point, from the medical aspect of the parasites, is that they do not 
remain fastened to one spot in the bowels, but suck first at one spot 
and then at another. Thus the patient loses blood directly to the 
parasites, and also, by numerous minute hemorrhages, into the intes- 
tine. It is probably this latter factor which occasionally gives to the 
stools of patients that peculiar reddish-brown tinge, and also their 
occasional bloody appearance. 
The injury to the intestinal wall does not stop with the bite. The 
wound foi-ms an excellent point of attack for bacteria, and the intes- 
tinal wall becomes thickened, thus losing, to a greater or lesser degree, 
the ability properly to perform its function. Aot only does the patient 
lose blood, but his power of assimilation is impaired, and the supply 
of blood-forming material is thus in part cut off'. Some authors also 
claim that the parasites produce a poison which acts upon the^ system, 
a view which is very strongly supported by certain clinical facts. 
It was stated above that hookworms are found in various animals. 
Now. the general rule mav be laid down that where these worms are 
present trouble may be expected. 
