PRESENT STATUS OF INVESTIGATION OF BEE DISEASES. 81 
dwelt on at length, we must pass on to the further consideration of this par- 
ticular organism. The first point to be determined in investigating its relation 
to foul brood was whether this was a new bacillus, unknown except in connec- 
tion with this disease of bees, or whether it was a more or less well-known 
form. To ascertain this point with regard to micro-organisms the microscope 
is of little use; recourse must be had to the study of their life history, more 
especially to their peculiarities of growth on different soils. Of all the ma- 
terials employed as cultivating media, Koch’s gelatinized meat infusion is 
the most useful for purposes of diagnosis. This is composed of an infusion 
of meat containing 1 to 8 per cent of pepton, 10 per cent gelatin, made neutral 
by carbonate of soda, and thoroughly sterilized. This material was first in- 
troduced with the view of having a highly nutritive solid and at the same 
time transparent medium on which to carry on pure cultivations, but it was 
soon found that owing to the remarkably diverse ways in which different 
micro-organisms grew in it, it could be used as a means of diagnosis of the 
kind of organism, a means more certain than any other which we at present 
possess. For purposes of diagnosis, as well as with the view of carrying on 
pure cultivations, this material is used in three ways. While the material is 
still fluid a small portion is poured into a number of pure tubes plugged with 
cotton wool, sterilized, and allowed to solidify. <A fine platinum wire, heated 
in a flame and allowed to cool, is dipped into the material containing the 
bacterium in question, and then, after the removal of the cotton-wool plug, is 
rapidly plunged down through the gelatin to the bottom of the tube and then 
withdrawn. The plug is reinserted and the tube kept at a temperature suita- 
ble for the development of most forms of bacteria, but not high enough to 
melt the gelatin. If growth takes place at this temperature it occurs either 
on the surface around the point of entrance of the needle, or along the needle 
track, or in both places, and the appearance of the growth varies remarkably, 
according to the different species of micro-organisins studied. The second way 
is to liquefy and pour out a little of the gelatinized material on micrescopic 
slides or on larger plates of glass which have been sterilized by heat. These 
plates are placed in glass vessels containing moist blotting paper to prevent 
drying of the gelatin and to protect them from the dust. After the gelatin 
has solidified the purified platinum needle charged with the bacteria is drawn 
rapidly over the surface of the gelatin. Bacteria are sown along the track, 
grow there, and the whole can be placed under a microscope and the charac- 
teristics of the growth studied with a low power. In the third mode a tube 
of the gelatin mixture is inoculated with a very minute quantity of the bac- 
teria. The tube is then placed in water at the body temperature to melt the 
gelatin. When the material is melted, it is thoroughly shaken up to diffuse 
the bacteria through it and, while still liquid, is poured out on sterilized glass 
plates kept in a moist chamber, as in the former case. Solidification very 
soon occurs, and the bacteria being caught at.various parts of the gelatin 
grow there in the form of groups or colonies, which can be observed under the 
low power of the microscope. I shall now describe the characteristics of the 
Bacillus alvei when cultivated in these three modes. 
(a) Test-tube cultivations.—lf an infected needle be plunged into a tube of 
gelatinized meat infusion in the manner described above, growth occurs both 
on the surface and along the needle track. On the surface the bacilli shoot out 
in all directions from the point of entrance of the needle, forming a delicate 
ramifying growth on the top of the gelatin; the characteristics of this growth 
will be presently described under b. Along the track whitish irregular shaped 
masses appear, which slowly increase in size and run together. In a few days 
