246 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
that their pnenmobacilli had become profoundly modified. They had lost 
the power of developing gas from glucose and lactose, and the growth 
on potato had become scarcely visible. Hence there was a striking 
approach towards B. typhosus, though they still continued to coagulate 
milk and to decompose lactose ; and this resemblance would furnish some 
support to the doctrine of Rodet and Roux, viz. that B. coli communis 
and B. typhosus are identical. The authors confirm the statement of 
Wurtz and Leudet as to the identity of the lactic ferment and B. aerogenes. 
Anthrax in Rats.* — Dr. K. Muller’s experiments with anthrax were 
made on rats, most of which were bred by crossing the white with the 
dark grey rat ; and he used white, black and white, grey-white, grey, 
and black rats, all of which therefore had different degrees of resistance. 
The food was chiefly bread, though one lot was confined to meat. The 
inoculation material was agar cultures and spleens of animals dead of 
anthrax. The subcutaneous inoculations were made with a loopful 
(1 mm. diam.) of agar culture in 1 ccm. of water. Sometimes the skin 
was snipped up without drawing blood, and some anthrax-spleen rubbed 
in. The author’s results may be summed up as follows. About four- 
fifths of the rats inoculated with small doses of anthrax die. Of 
the more resistant fifth, the majority succumb on further inoculation. 
Previous inoculation confers no immunity, indeed rather a susceptibility. 
Black rats are more resistant than grey, grey than black and white, 
and the latter than white; the degrees of resistance would be about 
— 2f — If — 1. Yet even among the white, and black and white 
races, individuals are found with a degree of resistance which would 
be represented by the figure 5 ; and taken generally, rats exhibit con- 
siderable difference in their resistance. The difference in individual 
resistance may be explained partly by breeding, and partly by feeding 
(this amounts to heredity plus environment). 
The appearances observed post mortem are roughly divided into two 
types, though there is no strict line of demarcation. In the white 
bread-fed rats the spleen is very large, often enormous, the liver is 
increased in size, and there is intestinal catarrh. In the dark races, 
fed on flesh, the spleen is little if at all enlarged ; there are serous, often 
sanious, exudations in the pleural sacs compressing the mottled lungs. 
In both cases the bladder is filled with bloody urine, and the kidneys 
are swollen. 
A third type, called chronic rat-anthrax, was observed in the parti- 
coloured animals who succumbed to the fourth, fifth or sixth inoculation. 
The chief characteristics were numerous small necroses, chiefly in the 
liver, but some in the spleen. 
The author found that alkaline methylen-blue was the most suitable 
stain, and the longer the disease had lasted, the more difficult it became 
to demonstrate the bacilli. The bacilli were always free and never en- 
closed in phagocytes. The author agrees that the organism of the rat 
is endowed with bactericidal properties, but these are neutralized by the 
metabolic products of the anthrax-bacilli. The immunizing principle 
is not associated with the serum, but is a product of the cells of the 
body. Though leucocytes may share in conferring immunity, it is 
* Fortschr. d. Med., 1893, pp. 225 and 309. See Centralbl. f. Bakteriol. u. 
Parasitenk., xiv. (1893) pp. 779-83. 
