811 
An Infection Experiment with Finger and Toe. 
great as when five tons are applied in the usual way. The cost of 
grinding is not a very serious item, but the result of future experi- 
ments must decide whether it is profitable or not. 
The experiment which has been described emphasizes the follow- 
ing practical points : — 
1. That finger and toe (locally known in the North as “grub ”) 
is an extremely infectious disease, and may be easily induced by 
inoculating a soil perfectly free from the disease — and holding 
much more than an average quantity of lime — with soil from a 
diseased field. 
2. That such diseased soil may be easily disinfected by lime, 
which points to the pathological phenomena being due to an organ- 
ism — presumably Plasmodiophora Brassicai. 
3. That farmers cannot be too careful to prevent soil or diseased 
roots being conveyed from a field that is diseased to another that is 
sound, or from a diseased part of a field to a portion originally 
unaffected. In this connexion the main points to be observed 
are : — 
(a) That no diseased roots be consumed by stock at the home- 
stead, for they are thus certain to get into the farmyard manure in 
greater or less quantity, and in it will be conveyed to fields which 
will probably be used for the cultivation of turnips. Such roots 
should be consumed either where they grow or on a permanent grass 
field. 
( b ) That carts or horses should on no account traverse a diseased 
field and afterwards go directly on to a sound one, for the soil thus 
conveyed on the wheels of the carts, or on the feet of the horses, 
will certainly contain disease germs, and will be the means of 
spreading the disease. 
(c) That the headlands should be carefully watched, so that 
disease may be stamped out by liming wherever it appears. As is 
well known, the headlands are generally more subject to the attack 
than any other part of the field, and in working the land the horses 
and agricultural implements carry away a certain amount of soil at 
every turning, and thus spread the disease all over the field. 
( d ) That unless conveyed mechanically the disease is not apt to 
spread far. In the above experiment plots 1 and 1a, which did not 
contain a single diseased root, were situated within 27 inches of 
plots 2 and 2a respectively, which contained only two sound roots 
between them, and yet this narrow interval was sufficient to prevent 
the passage of the disease germs. Similarly in the case of plots 6a 
and 7, the roots on the former were almost free from attack, while 
those on the latter were nearly annihilated. 
William Somerville. 
The Durham College of Science, 
Newcastle-upon-Tyne. 
