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 3J lines in diameter, and presents to the 

 naked eye the appearance of a delicate and close network, arising 

 from the numerous areolae 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 areolae, the further deposit takes place in a fibrous or line-like 

 course from the parietes of the areolae of the primitive osseous rete, 

 in the interspaces of the cartilage- cells nearest to, or in contact with 

 the sides of the areolae. At this period the cells shoot out or extend 

 their canaliculi between the fibrillae just formed, and then the cell- 

 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 fibrillae, and with the fibrillae 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 in 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 



