ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
773 
Behaviour of Mobile Micro-organisms in Running Fluids.* — Dr. 
Roth lias noticed that mobile micro-organisms which generally move 
about in an apparently aimless way have a decided tendency to swim 
upwards in running fluids. He considers that this is a perfectly 
mechanical phenomenon, and that bacteria move forward in a given 
direction until they happen to knock up against something. The 
current then acts on the free posterior end, the front end becomes free 
and is turned against the current, so that the movements of the organism 
are directed upwards. In the observations dental mucus was used, for 
with this a current can be easily induced if at one side of the cover-glass 
be placed a little water and a piece of blotting paper at the other. 
Obstacles, consisting of minute bodies, were placed in the fluid for 
the bacteria to impinge against, and these were found to impart an 
upward direction to them. 
The author concludes from his observations that micro-organisms of 
elongated shape when moving in the direction of their length in a running 
fluid tend to move upwards, provided the current is suitably rapid and 
the stream sufficiently narrow. The author applies the same explanation 
to the upward course of the spermatozoa to the ovaries. 
Defence of the Organism against Microbes after Vaccination.^ — 
Dr. Sanarelli has been studying the question of the bactericidal state of 
the vaccinated organism by the aid of the disease produced by the Vibrio 
Metschnikovi, a disense easily inoculable on birds and on guinea-pigs, in 
which it produces the symptoms and phenomena of a very acute septi- 
caemia. From the fact that the experiments were conducted under the 
supervision of M. E. Metschnikoff, it scarcely needs to be said that the 
author s position is defensive of phagocytosis and attacks humoralism 
under its three different aspects. These three hypotheses are known as 
the bactericidal, the attenuating, and the anti-toxic. By the first, 
acquired immunity is ascribed to the power the body-juices possess of 
killing the invading organisms ; by the second, to their ability to remove 
the pathogenic properties of the microbes ; by the third, to their 
neutralizing action on the toxins secreted by the bacteria. 
The general conclusions of the author concerning the result of 
infection in the case of vaccinated animals are that microbes can 
develope without difficulty even in the serum of vaccinated animals, 
where, instead of becoming attenuated, they acquire a still greater viru- 
lence. The serum of vaccinated animals is not endowed with an anti- 
toxic property and does not prevent the formation of microbic toxins. 
The vaccinated animals escape infection owing to the efficient action of 
the phagocytes. 
With regard to the case of animals treated with serum obtained from 
vaccinated animals, the author finds that this serum is endowed with 
eminently preventive properties, and animals do not take the disease if 
inoculated with this serum. The serum seems to w r ork by stimulating 
the leucocytes both in the general circulation and at the site of inocu- 
lation, but the destruction of the microbes is always effected by the 
phagocytes. 
It is interesting to note that the action of the phagocytes is paralysed 
* Deutsche Med. Woehenschr., 1893, No. 15. See Centralbl f. Bakteriol. u. 
Parasitenk., xiii. (1893) p. 755. f Ann. Inst. Pasteur, vii. (1893) pp. 225-59. 
