112 PHYSIOLOGY AND DISEASES OF VEGETABLES. 
Thus, I conceive that, while it is fully demonstrated that, 
in certain cases, pus may pass into the circulation without 
producing any very manifest inconvenience, that, in others, 
it will produce coagulation of the blood in the lining vessels, 
and a train of consequent symptoms which will vary according 
to the locality in which such stagnation has taken place. 
What the circumstances are which, in one case, will deter- 
mine this effect, and in another not, will form the subject of 
a separate inquiry. For the present, I must content myself 
with having shown, as I believe, from independent evidence 
derived from experiments undertaken to illustrate other and 
different views, that the doctrine which I first published in 
1849 is not devoid of foundation; and that the propositions 
which I then endeavoured to establish, — namely, that pus 
and some other morbid fluids, when mixed with the blood, 
have a tendency to produce its coagulation, and that this 
tendency is often more quickly manifested in the body than 
out of it, — have been fully demonstrated. 
18, Dover Street, Piccadilly ; 
Dec. 13tb, 1853. 
ON THE PHYSIOLOGY AND DISEASES OF VEGETABLES, 
PARTICULARLY IN REFERENCE TO THE DESTRUCTION 
OF HOP PLANTS. 
9 
BASED ON AN ESSAY WHICH WAS AWARDED A PRIZE BY THE 
ROYAL AGRICULTURAL SOCIETY OF ENGLAND, TO E. J. 
LANCE, IN THE YEAR 1847. 
The inquiry will be divided into the following heads : 
1st. The natural history of the hop-fly [aphides) in all its 
stages. 
2d. The best remedy against its attack, and preventive 
against its ravages, by growing other seed in gardens, or by 
other means. 
3d. Whether the same fly attacks other plants. 
4th. Whether the disease on the hop and other plants, 
called “ honey/’ is occasioned by the hop-fly, or arises from 
some other cause. 
1st. On the natural history of the hop-fly . It is presumed to 
be the aphides , that is meant by the term “ hop-fly,’ 5 as there 
is another insect, the flying beetle, altica, which is at times 
very destructive to the first growth of the hop plant. 
The hop-fly plant lice, dolphin, vine-fretter, are local names 
