ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 327 
being a 2 per cent, pepton solution, with 1 or 2 per cent, of gelatin. 
The optimum temperature was 37°, and growth took place under aerobic 
and anaerobic conditions. Cultures were fatal to mice and guinea pigs, 
but not to pigeons, the animals dying from pyogenic septicaemia. Experi- 
ments as to the resistance of the plague bacillus showed that the best 
method for disinfecting was moist heat at 100°, i. e. steam. 
According to Ur. W. M. Haffkine,* the plague bacillus is easily 
recognised by a stalactite growth in broth. The broth, richly inoculated 
with the bacillus, must be kept in an absolutely quiet position, as the 
slightest jar destroys the reaction. In from 21-48 hours flakes appear 
underneath the surface, forming little islands of growth ; from these long 
stalactites grow downwards, the liquid always remaining clear. If after 
5 or 6 days the flask be shaken, the whole growth falls to the bottom, 
the islands retaining their form, while the stalactites are perfectly dis- 
integrated. The bacillus is also recognisable by involution forms on 
agar. The medium must not contain glycerin, must not be freshly pre- 
pared, the surface must be perfectly dry, and the reaction alkaline. The 
surface must be inoculated abundantly. In usually from 3 to 4 days 
the individual microbes swell up, forming large round, oval, or pear- 
shaped bodies, which eventually are quite unstainable. The bacilli 
become unrecognisable, acquiring the appearance of a yeast cell or an 
alga. The swelling may continue until the body is twenty tirms larger 
than the original bacillus. Similar forms are demonstrable in the tissues 
of animals dead of the disease, and then they resemble modified blood- 
corpuscles, or disintegrated tissue-cells, or stained drops of albumen. 
Epidemic of Botulism.f — By means of a bacteriological examination 
of fragments of sausages suspected of causing an outbreak of botulism 
among troops in a Belgian artillery barrack, Dr. Dineur isolated three 
varieties of coli bacillus, one of which (variety A) was also isolated from 
the body of a mouse fed on the same sausages. By continued cultivation 
the virulence of this variety A was reduced and even abolished. The 
source of the bacteria was probably the flesh of an infirm or diseased 
animal, from which the sausages Were made. 
Bacteria normal to Digestive Organs of Hemiptera4 — Prof. S. A. 
Forbes gives a preliminary account of the caecal appendages of certain 
Hemiptera, which were found to be invariably loaded with myriads of 
bacteria, differing in genus and species in the different insects, but always 
confined to these organs. The bacteria were cocci and bacilli ; they 
responded to the ordinary stains, and were cultivated in fluid and on 
solid media. 
Variation of Bacteria from Age.§ — Dr. H. G. Dyar replanted the 
“ new species ” of bacteria described by him after intervals varying from 
one to two years, for the purpose of ascertaining if there had arisen any 
differences of form and function. The conclusions arrived at from these 
replantings are : — (1) species under long cultivation tend to be con- 
stant in their characters ; (2) some species lose in vigour; (3) some gain 
* Brit. Med. Journ., 1897, i. p. 1461. 
t Bull. Soc. Beige de Microscopie. xxiii. (1896-7) pp. 47-66. 
X Bull. Illinois State Lab., iv. (1895) pp. 1-7. 
§ Trans. New York Acad. Sci., xv. (1895-96) pp. 148-53. 
z 2 
