DISEASES AND ENEMIES. 
545 
The absence of dumb-bell forms, and the distinctly 
oval shape of what I presently found to be spores 
of the associated bacilli, at the first arrested my 
attention. Now, possessing myself of an infected 
stock, so that the course of the disease could be 
traced, I submitted the body of a grub recently dead 
to the scrutiny of the microscope, and here I was 
delighted by seeing hundreds of bacilli actively 
swimming backwards and forwards, and worming their 
way amidst degenerate blood-cells and fat-globules, 
as seen at D, Plate I. ; while some of these bacilli 
had already begun to sporulate, as may be traced by 
a central enlargement. Securing other larvae of suspi- 
cious colour only, I discovered that, at the incidence 
of the attack, the bacilli do not break up, but grow 
in thin chains (leptothrix), as at C, Plate I. 
The examination of a larger number of larvae, not 
only from the stock referred to, but from combs 
coming from various parts of Great Britain and 
Ireland, showed most conclusively that each individual 
affected contains in its blood bacilli of an average 
length of in., and diameter of 4000 - 0 - in., mostly 
swimming with a corkscrew-like movement,* the 
termination of the rod, as seen in end view, constantly 
describing a small circle; that when the disease is 
establishing itself, leptothrix forms are common, some 
of them even reaching y^in. in length; that these 
then break up into bacilli, which rapidly multiply, 
so as to crowd the fluids and tissues, as may 
be judged from an exact drawing of a tiny blood 
* I have only recently obtained sight of the flagella (B, Fig. 123), by 
which the movement is caused. 
VOL. II. 
2 N 
