774 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
if the organism be cooled ; then they no longer react to the stimulus of 
the preventive serum, and the vaccinated animal inevitably succumbs to 
the infection. 
Resistant Germs in Gelatin.* — Dr. L. Heim has found that gelatin 
such as is used for the preparation of nutrient media contains germs, 
highly tenacious of life, and that these develope after the medium has 
been carefully sterilized. Isolation experiments proved that those 
germs which resisted the action of steam were two species of endogenous 
spore-forming bacilli distinguishable by their cultural characters. The 
resistance of the smaller of the pair was overcome by 3 hours ex- 
posure to steam, while the larger bacterium took from 5-7 hours to 
die under similar conditions. After several cultivations, the resistance 
to heat seemed to diminish, and when exposed to the action of steam 
with tension of the atmosphere, they did not grow, for the spores were 
destroyed in the sterilizer in 15 minutes. 
It is probable that during the manufacture the gelatin became con- 
taminated with earth. 
Thermotaxis of Micro-organisms and its Relation to Chill.t — 
Prof. S L. Schenk considers thermotaxis to be a vital property of 
bacteria, exhibited when there is a difference of temperature amounting 
to 8-10° C. Under these conditions heat acts as an irritant upon bacteria, 
causing them to move towards the warm point. Bacteria which are free 
and independent present the phenomena of thermotaxis more clearly 
than those united together in chains. When, however, micro-organisms 
have been kept for some time in a room, at a low temperature, and are 
afterwards placed in a room with a higher temperature, they do not at 
first develope with their full energy, and do not manifest their full effect. 
As they become acclimatized to the higher temperature the decrease in 
developmental energy and virulence disappears. Chills are separable 
into two groups, those unassociated with bacterial influence, and tho^e 
chills which are to be regarded as the expression of an infection. In 
infection chills the disease does not manifest itself immediately after 
the occurrence of the lesion, but in the other group the morbid phenomena 
appear soon after the action of the irritant. When a man enters a cold 
room a bacterial stream sets in towards him by reason of his higher 
temperature, and thus induces a chill. For the occurrence of an 
infection-chill two conditions are necessary, first a difference of tempeia- 
ture which causes a microbic current to set towards the warmer point, 
and secondly, the penetrability of the skin or mucosa to microbes or 
some other mode of entrance of the bacteria into the body. 
Action of Gravity on Bacterium Zopfii4 — Mr. R. Boyce and Mr. 
A. E. Evans describe a pecular “ pinnate ” growth of this bacterium 
which could only be obtained in gelatin cultures which wei e kept vertical 
or nearly so. The mode of growth appeared, from experiment, to be due 
to the action of gravity. 
Organism of the Root-tubercles of LeguminosseJ — Prof. G. F. 
Atkinson gives a careful review of the literature of this subject, and an 
* Centralbl. f. Bakteriol. u. Parasitenk., xiii. (1893) pp. 649-50. 
t Tom. cit., pp. 33-43; 
J Proc. Roy. Soc., liii. (1893) pp. 48-50. 
§ Bot. Gazette, xviii. (1893) pp. 157-66, 226-37, 257-66 (3 pis.). 
