242 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
fluence of Physical Conditions on the Life of Micro-organisms.* — 
Drs. E. Bonardi and G. G. Gerosa have made a series of experiments on 
the susceptibility of micro-organisms to environmental influence. They 
start with a useful summary of the results already reached by others, 
and then expound their own. In solutions of flesh-extract and peptone 
the density of the fluid has no effect on form ; in gelatin the microspores 
are found only in the denser solutions ; in flesh-extract the multiplication 
is more abundant and rapid in the less dense solutions, in gelatin the 
reverse is true ; in flesh-extract of whatever density only Schizomycetes 
develope, in gelatin Penicillium predominates, in peptones both occur 
equally. The minimum temperature at which microbes will develope 
varies with the quality and density of the organic solution ; in flesh- 
extract of slight density they multiplied for eleven days at 5°, but when 
the density was increased the temperature had to be raised to 10°, while 
in gelatin they remained sterile for months at 25°. A solution of flesh- 
extract of slight density was sterilized at 50°, but a denser solution 
required 60°. After three days at 79°, granulations appear which are not 
absolutely distinguishable from the indubitable organisms. In all the 
solutions, Bacillus subtilis prevails at higher temperatures above 30°, 
B termo at lower, but both show themselves in manifold instable forms. 
In favourable solutions of flesh and peptone, B. subtilis resisted for 
twenty -four hours temperatures of 79° and even 100°. Heating flesh- 
extract for two or three hours in a Papin’s stove at 120°-130° did not 
hinder the appearance of spherical organized bodies. Carbonic acid 
gas and nitrogen only retard development, magnetic and electric 
influences have likewise a retarding influence, and this is very markedly 
the case with sunlight. 
Red Nitro-indol Reaction as a Test for Cholera Bacilli.f — Herr R. J. 
Petri considers that the red nitro-indol reaction is of diagnostic value for 
ascertaining the presence of cholera bacteria. It would appear, however, 
from his experiments that this value is rather scientific than practical, 
inasmuch as the test must be used in combination with plate-cultivations 
and other suitable methods for recognizing the micro-organisms, and 
also that it is essential that pure cultivations only should be employed, 
contents of the intestinal canal and the like being unsuitable. 
The reaction in question is the production of a red colour in the cholera 
vibrio after the addition of sulphuric acid ; a reaction which results in 
the formation of indol and nitrite. The author confirms the original 
observation that the reaction takes place on media containing pepton. 
After the addition of the acid, 10 drops to 6 ccm. of the nutrient medium, 
the red reaction begins to appear after four hours’ incubation, attaining 
its maximum in twenty-four to forty-eight hours, after which it dies away. 
A similar red colour was obtained by the reagents used with other 
bacteria, a fact which, as alluded to above, seems to deprive this test of 
much of its so-called value. 
Tumours in Animals4 — M. A. F. Plieque, in discussing the 
aetiology of tumours, lays it down that it is of great importance to 
* Atti R. Accad. Lincei — Mem., v. ( 1838 ) pp. 332-73. 
t Arbeiten a. d. Kai9. Ges.-Amte, vi. p. 1. See Centralbl. f. Bakteriol. u. 
Parasitenk., viii. (1890) pp. 152-3. 
X Rev. <le Chirurgie, ii. (1890) No. 7. See Centralbl. f. Bakteriol. u. Parasitenk., 
viii. (1890) pp. 148-9. 
