764 INTUSSUSCEPTION OF THE SMALL INTESTINES. 
sequently, that at one part it may be excited to increased 
action, while at another, even closely adjacent to it, it may be 
very sluggish in its movements. I can also conceive that 
the supply of nerve force may be so irregular that the con¬ 
traction of the circular order of fibres at one part will be un¬ 
usually prolonged, while that of the longitudinal fibres will 
be comparatively of short duration. Such irregularities 
would lead to intussusception, which may occur in the fol¬ 
lowing way, viz., a contracted portion of intestine may 
protrude into a dilated part posteriorily, or even anteriorily, 
to it (depending upon whether this abnormal action is pro¬ 
gressive or retrogressive), dragging with it a portion of the 
mesentery. The circular fibres of the outer part of the 
bowel, forming, as it were, the sheath, immediately contract 
upon the invaginated position, and prevent its return. It 
is important to bear in mind that the part of the bowel thus 
affected will, by its being folded upon itself, have three 
thicknesses of its coats in apposition to each other—this is 
at once seen by inverting a portion of the finger of a glove— 
and, further, that there are four surfaces in contact with each 
other, viz., two peritoneal and two mucous. Now, in con¬ 
sequence of the impediment to the return of blood from the 
vessels of the invaginated intestine and mesentery, extensive 
serous effusion takes place, resulting in swelling and intense 
redness, or even blackness, from the blood-vessels being so 
much engorged. The most serious result of this effusion is 
that the plasma of the effused serum glues, as it were, the 
surfaces of the inverted bowel firmly together, preventing 
thereby the possibility of its returning again to its normal 
position. 
Other parts of the intestines may become similarly affected, 
either at the same time, or subsequently. If the former, the 
lesions would be the same in character; but if the latter, the 
morbid changes would not be so intense. These phenomena, 
however, are only discovered on making a post-mortem ex¬ 
amination. The invaginated portions of the bowels of the 
dog examined by me distinctly showed that the vessels of 
the one anteriorly placed were much more strangulated than 
those of the others. This fact suggested to me the probability 
of the invagination having occurred primarily at one place 
only, and that it was subsequently followed bv the others 
and also that the affection was progressive, and not retrogres¬ 
sive. This, however, was not easily to be determined by 
the appearances of the parts. 
