163 
VEGETABLES, EEUIT, AND WATER AS SOURCES 
OF INTESTINAL WORMS. 
By T. SPENCER COBBOLD, M.D., F.R.S., F.L.S., 
LECTUHER ON COMPARATIVE ANATOMY AT THE MIDDLESEX HOSPITAL. 
E ESPECTING animal food as a source of parasites, it is 
not difficult for the helminthologist to explain how 
certain well-known species of entozoa aro introduced within 
the human body ; but in the case of vegetables he cannot 
speak with equal preciseness, seeing that the subject is 
surrounded with many and great difficulties. As a general 
proposition, however, it may be truthfully averred that 
entozoa are frequently introduced into our stomachs along with 
vegetable food; but we are not thereby warranted in the con- 
clusion that the parasites existed within the parenchyma or 
tissues of the vegetable substances thus swallowed. Neither, 
on the other hand, are we yet in a position to state with cer- 
tainty that the vegetable matters in question did not actually 
harbour the parasites within their tissues. In various plants 
I have, from time to time, noticed free nematodes within their 
parenchyma ; and in certain instances I have entertained the 
belief that they were in the sexually immature condition. 
Whether any of them were the larvae of, and therefore speci- 
fically identical with, certain well-known forms of human 
entozoa, can only be a matter of conjecture ; nevertheless, to 
I indicate to what extent particular human parasites are clearly 
I referable to the various sources under consideration, I invite 
I attention to the following facts ; — 
i Wateeceesses, &c. — Under this head may be included 
I various pondweeds, and different kinds of vegetable debris, 
i fioating in ditches, lakes, and semi-stagnant waters; for, even 
i in cresses prepared for the table I have noticed portions of 
ij frog^s-bit {Hydrochar is morsus ranee) and other weeds. These 
1 vegetables have often small mollusks and other aquatic 
animalcules adhering to them, and if the former are eaten in an 
' imperfectly washed state, it will consequently happen that the 
latter are swallowed during the meal. Small mollusks are 
known to harbour larval parasites, more or less like the one 
here represented (fig. 1), in prodigious quantities, and there- 
fore it is not unreasonable to conclude — bearing in mind the 
extent of our knowledge of the transformations which these 
M 2 
