68 
at the evidence furnished by the various cases of H. nana on record 
shows that severe symptoms are of frequent occurrence. As an addi- 
tional support of the fact that the size of a tapeworm is no index of 
the amount of damao'e it mav do, a number of instances miaht be oiven 
in which small tapeworms are occasionally even a serious menace to 
life. In such instances, however, it is usually the case that the number 
of worms present is so great that mechanical obstruction alone, not to 
speak of the loss of nutrition to the host, is sufficient to explain the 
severe results: or it may happen, as occurs in the case of a certain 
comparatively small tapeworm of the chicken, that the parasites bore 
deeply into the submucosa and almost or entire!}' penetrate the intes- 
tinal wall, and in this way give rise to very serious effects. 
In considering’ the manner in which llyinenolepis nana affects its 
host, the question of mechanical obstruction may be left out of account, 
unless the parasite is present in overwhelming numbers when it would 
be of importance. 
Since each worm has a se'i^arate point of attachment to the intestine, 
it is likely that considerable irritation will result if many are present. 
The rather extensive movements of the larger tapeworms while extend- 
ing or contracting themselves give rise to a certain amount of irrita- 
tion, but in the case of JL nana. it does not, a priori, seem probable 
that its movements would have much of an irritating effect, unless 
the worm were present in very large numbers. The assumption that 
more or less irritation of the intestine is caused by the presence 
of JL nana is supported by the fact that diarrhea and other intestinal i 
derangements, and various reffex symptoms commonly attributed 
to intestinal irritation, occur frequently. As to the extent of the 
local effects of the parasite under discussion our knowledge is lini- ; 
ited. Although some evidence has been adduced, intended to show 
that pathological changes occur which are of considerable importance, 
the balance of evidence seems to indicate that organic changes of the 
intestine, if occurring at all, are very slight. 
Innes (1898) speaks of bloody extravasations found on the mucosa of 
the ileum which he considers might possibly ha^’e marked the points 
of attachment of the tapewoi’ms (Case No. 8). 
According to Grassi (188Td) the worms were found to have bored 
deeply into the mucosa, and to have caused considerable alteration, , 
but the nature of the change is not specified. 
At the post-mortem examination of a case (No. 9) of Ilymenolepis 
nana^ in which dOO specimens were found in the ileum, Visconti & 
Segre (1886) noticed that the mucosa throughout the small intestine , 
was tumefied, hyperemic, and covered with a thick layer of grayish i 
mucus, through which the worms were scattered. The greater part i 
of the solitary follicles were tumefied. Microscopic examination of a 
portion of the ileum showed the mucosa swollen and richly infiltrated 
