MICROSCOPY. 501 
ings under high powers. The large cavity between the frustules is 
regarded as equivalent to the embryo-sac of higher plants, and 
the formation of new individuals has been observed within it. An 
alternation of generation is indicated by the observations made. 
Orterxn or Cancerous Derposits.— Dr. J. J. Woodward dis- 
cusses this question in a report to the Surgeon General. His 
observations of structure do not differ materially from those of 
other recent observers, though the cell walls of the cancer cylin- 
ders, described by Keester, he is able to detect in only a portion 
of the cases. He reviews the theory of Kester who regards the 
nucleated cylinders as transformed lymphatics, and of Thiersch 
who explains them as outgrowths from the lower layer of the 
epidermis and from the epithelium of the glandular apparatus. 
The latter view was originally applied to epithelial cancer, but 
has been extended by Billroth to cancer generally. Dr. Wood- 
ward is manifestly unwilling to commit himself to any theory, 
but rather favors Keester’s on account of the well known similar- 
ity of the morbid growths when affecting different organs, and on 
account of the manner in which the cell cylinders anastomose, 
Which points rather to the lymphatics than to the gland: tissue. 
He Seems not unwilling ‘to regard the cancer cylinders as COR- 
sisting of transformed white corpuscles accumulated in the lym- 
Phatic passages. The presence or absence of a cell wall he 
justly considers unimportant, it being only an indication of age 
m cells which, according to our present knowledge, consist origi- 
nally of only a nucleus embedded in a mass of protoplasm. 
Tue “Nerve” or tae Toors.— Mr. T. C. White has read 
: Y interesting paper on this subject before the Queckett 
Microscopical Club. Though considering it a painful subject, 
and not to be touched upon except very lightly, he nevertheless 
considers it interesting to know something of its structure aní 
es. 
The pulp, or so called nerve of a tooth, should be obtained from 
à tooth of the temporary set removed in a state of health to make 
room for the advancing permanent set. A longitudinal groove is 
a be filed around the tooth, which is then to be very carefully 
mashed, and then split with a pair of wire nippers. The pulp 
Will thus be fully exposed, and may be stained by soaking for 
Wenty-four hours in an ammoniacal carmine solution as recom- 
