74: Miscellaneous. 
MISCELLANEOUS. 
On the Development of the Purkinjean Corpuscle in Bone. 
Schwann, in his ‘ Mikroskopische Untersuchungen,’ considers that 
the Purkinjean corpuscle of bone is derived from the pre-existing 
cartilage-cell, and that the canaliculi are prolongations, or protru- 
sions of the cell-wall. Many later authors, among whom are Gerber, 
and Todd and Bowman, express the opinion that it originates in the 
nucleus of the temporary cartilage-cell, and Tomes entertains the 
idea, that after the formation of the osseous tubes, in the process of 
ossification, the latter are filled up by a deposit of osseous granules, 
and while this deposit is going on, small cells are left, which are 
the rudimentary Purkinjean corpuscles. Henle thinks them to be 
the cavities of cells, the thickened walls of which are pierced by the 
canaliculi. Hassall confirms the view of Schwann, by stating, “ the 
bone-cells (Purkinjean corpuscles) are to be regarded as complete 
corpuscles, the canaliculi of which are formed by the extension of 
the cell-wall, which is proved by watching the formation and de- 
velopment of bone.” 
The opinion of Schwann and Hassall I can fully corroborate from 
my own observations upon an ossifying frontal bone, from a human 
embryo measuring 2 inches from heel to vertex. Each lateral 
half of the bone is about 34 lines in diameter, and presents to the 
naked eye the appearance of a delicate and close network, arising 
from the numerous areole occupied by temporary cartilage. ‘The 
frontal and orbital plates, it is worthy of incidental remark, at this 
period are nearly on a plane with each other, or are connected to- 
gether at a very obtuse angle along a central, transverse, crescentic, 
raised line, the rudimentary supra-orbitar ridge. 
The mode of development of the Purkinjean corpuscle, as noticed 
upon the upper or posterior border of the os frontis, is briefly as 
follows :—After the primitive ossific rete has been formed from the 
deposit of the osseous salts, enclosing groups of cartilage-cells in 
the areole, the further deposit takes place in a fibrous or line-like 
course from the parietes of the areole of the primitive osseous rete, 
in the interspaces of the cartilage-cells nearest to, or in contact with 
the sides of the areole. At this period the cells shoot out or extend 
their canaliculi between the fibrille just formed, and then the celi- 
wall and continuous walls of the canaliculi fuse with the translucent, 
homogeneous, or hyaline substance of the cartilage existing between 
the cells and the osseous fibrillee, and with the fibrille themselves, 
by the deposit of the osseous salts. The period of the formation of 
the canaliculi appears to be quite definite, occurring during the de- 
posit of the osseous salts, and not before. To such an extent is this 
the case, that I noticed im several instances cells which had formed 
their canaliculi upon the side which was ossified, while upon the 
other side I could not distinguish any trace of them. 
During the whole time of the formation of the Purkinjean cor- 
puscle, the nucleus remains unchanged ; at least no change is per- 
ceptible in it beneath the microscope ; and by applying tincture of 
iodine to the preparation, which turns the nucleus brown, I was able 
