30 
PROGRESS OF MICROSCOPICAL SCIENCE. 
fessor Politzor gave tlie result of some investigations which he h-I 
recently made into the anatomy of the ear, which was thus given in 
the ‘ Medical Record,’ December 2. He finds that, in newly-born 
children, the cavity of the pyramid containing the stapedius muscle 
is separated only at the upper part by osseous tissue from the canal 
through which the facial nerve passes, while the lower part of the 
cavity communicates freely with the same canal, and thus allows, at 
this spot, the muscle and nerve coverings to come into actual contact 
with each other. In the adult, the amount of direct communication 
between the cavity and canal is very various, ranging from a small 
opening sufficient for the passage of the nerve to the stapedius, to a 
large irregular opening. The styloid process, he avers, arises from a 
cartilaginous body, which not only in the foetus, but also in the newly- 
born, is to be found as an isolated cartilaginous formation ; and the 
upper end of the process does not terminate at the external visible 
base, but passes through a thin osseous lamella along the posterior 
wall of the tympanic cavity, reaching as far as the eminentia stapedii. 
In the adult, the process is sometimes solid, sometimes hollow, hut 
generally there is a cellular structure with or without a central canal. 
Action of Electricity on Frog’s Spawn. — M. Onimus, in a recent 
communication to the Societe de Biologie, of Paris, states that by 
electrifying the eggs of the frog, the development of those which are 
in connection with the negative pole will be accelerated, whilst the 
hatching of those in connection with the positive pole will be either 
retarded or stopped. 
What is a Bacterium ? — Dr. W. A. Hollis has written a paper lately 
(Nov. 21) on the above question which may be of some interest to our 
readers. He says that the question, What is a bacterium? is thus 
answered by Ehrenberg in his great work on Infusoria : * “ Animal 
e familia Yibrioniorum divisione spontanea in catenam filiformem 
rigidulam abiens.” Dujardin accepted this definition without altera- 
tion, although he modified somewhat the other genera of- the family. 
The derivation of the word itself (from BaKrypLov, a little rod) corre- 
sponds well with the characteristic features of the organism above 
given. For several years the accuracy of Ehrenberg’s definition was 
unquestioned ; eventually, however, from the observation of the 
behaviour of these organisms with certain chemical reagents, and 
mainly also from the elaborate researches of Professor Cohn regarding 
their morphology, their animal nature was disputed. It was found 
that they were unaffected by boiling with potash water, and they were 
further said to behave somewhat as cellulose does when they were 
treated with sulphuric acid and iodine, although from their extreme 
minuteness any changes which take place in their tissue under such 
conditions are very difficult to observe. 
For many years past Professor Cohn, of Breslau, has published in 
occasional papers the results of his investigations on the subject. He 
has made one great step in advance of previous observers in ascertain- 
ing so much of the history of the bacterium as that it arises from the 
* ‘ Die Infusions-thierchen,’ 1838, p. 77. 
