69 
with lymphoid cells. The connective tissue of the siibmucosa was 
sclerosed and thickened. 
Mingazzini (1899. pp. 598-599. 603) has recently made some obser- 
vations upon the mode of attachment of Ilymenolepis nana to the in- 
testine of the rat, which are of interest in this connection. He found 
that the rostellum in the living state, when the worm is attached to 
the intestine, is always extruded, and penetrates deeply into the lumen 
of a glatKl of Lieberkuhn: it may reach as far as the bottom. Only 
a very slight alteration is produced in the epithelium of the gland, ex- 
cept at the point where the surface of the rostellum and the epithelium 
are in contact. The hooks on the anterior part of the rostellum pene- 
trate only the epithelial cells, frequently producing some alteration 
in their shape and contents and occasionally entirely destroying them 
over a A^ery small area. At the points where the suckers and the epi- 
theliiun are in contact there are sometimes found little elevations in 
the latter, corresponding to the caAuties of the suckers. Grassi and 
Calandruccio. after examining the intestines of rats infected with H. 
nana^ asserted that at the point of attachment there seemed to be an 
abnormal number of leucocytes in the connective tissue. Mingazzini, 
howeA'er, found, upon examining the same preparation used by these 
authors, that the connective tissue of the tunica propria in the region 
of the point of attachment of the worm Avas entirely normal as to the 
number of leucocytes. If II. nana acts the sanie in the human in- 
testine as in that of the rat, it is not possible. Hiugazzini believes, to 
attribute to this cestode the A^ery grave and extensAe anatomical 
changes in the mucosa of the human intestine, which were noticed by 
Visconti and Segre, and Grassi. The fact that in the great majority 
of cases of II. nana reported, the individuals affected exhibit no 
phenomena of disturbance, is also considered by ^Mingazzini an argu- 
ment against the occurrence of anatomical changes of importance. He 
believes it is therefore justifiable to consider that the lesions referred 
to which haA^e been noticed in the human intestine are pathological 
conditions concomitant with, rather than due to, the presence of the 
parasite. The nervous phenomena, he adds finally, which sometimes 
appear in children infected with II. nana. and are cured by the elimi- 
nation of the parasite, are perhaps due to a toxin AA'hich. while not 
altering the structure of the intestine, acts upon the central neiwous 
system. 
The toxic eff ects of intestinal parasites upon their hosts is a question 
AAuth regard to which little is known, but sufficient Avork has been done 
to show that in some instances parasites elaborate substances which 
are distinctly poisonous when absorbed. In a reAuew of the results of 
various iuA^estigators bearing upon this point, LinstoAv (1896b, p. 189) 
expresses the following opinion: 
The helminths eliminate a poisonous substance, a toxin or a leucomain, as is the 
case with the pathogenic micro-organisms and, as in the latter case, it is not the me- 
