278 



OP THE PRIMARY TISSUES OP THE HUMAN BODY. 



it is only with the very first stage of the process, that the cartilaginous matrix 

 has any concern. 1 



267. In the formation of a long bone (Fig. 71), we usually find one centre of 

 ossification in the shaft, and one in each of the epiphyses; in the flat bones, 

 there is one in the middle of the surface, and one in each of the principal pro- 

 cesses. The ossification usually proceeds to a considerable extent, however, in 

 the main centre, before it commences in the extremities or processes ; and these 

 remain distinct from the principal mass of the bone, long after this has acquired 

 solidity. During the spread of the ossifying process, the cartilaginous matrix 

 continues to grow, like cartilage in other parts; but after the bony deposit has 

 pervaded its entire substance, in the manner just described, a change takes place 

 in the method adopted. The osseous laminae, that subdivide the whole texture, 

 are removed by absorption from the interior of the shaft, so as to leave the great 

 central medullary cavity ; whilst on the other hand, they receive progressive 

 additions in the external portion, which is thus gradually consolidated into the 

 dense bone, that forms the hollow cylinder of the shaft. This consolidation is 

 effected by the deposit of a series of concentric laminae, one within another, on 

 the lining of the Haversian canals. The bone continues to increase in diameter, 

 by the formation of new layers upon its exterior ; and Dr. Sharpey has pointed 



Fig. 70.* whilst the translucent intercellular matrix remains un- 



changed. The average diameter of the cartilage corpuscle is 

 about yg'g-ffth of an inch and the nucleus yyyyth of an inch. 

 Upon examining this border of the bone, Dr. Leidy noticed 

 a system of reticulated osseous fibres proceeding from the 

 primitive ossific rete into the intercellular substance of the 

 cartilage cells, apparently by a deposit of earthy salts, in a 

 linear direction. In such position, he observed the cartilage 

 cells had already protruded, or had connected with them, 

 the canaliculi ; and these appear at this time only, because, 

 several cells (Fig. 70*, e), noticed at the edge of the primitive 

 bony rete, and partly enveloped in the osseous deposit, had 

 the canaliculi passing into the latter, whilst on the unossified 

 or cartilaginous side, none had yet been developed, The cell 

 wall has until now apparently remained unchanged, but com- 

 mences to blend or fuse itself with the intercellular substance, 

 and with the secondary osseous fibrillae. The Purkinjean cor- 

 puscles, or lacunae (d), which are perfectly formed in the osse- 

 ous structure, at this time have the same diameter, or nearly 

 so, as the cartilage corpuscle from which they originated, and 

 they still contain a granular nucleus, readily brought into 

 view by iodine, which corresponds to that of the cartilage cor- 

 puscle, and has about the same measurement. At a later 

 period the nucleus of the Purkinjean corpuscle appears to 

 dissolve away.* ED.] The various gradations of the calci- 

 fying process in a fibrous tissue may be very well seen in the 

 ossified tendons of the legs of many Birds. 



Represents a portion of the border of the os frontis from a human embryo, measuring two inches in length, 

 very highly magnified, a. Portion of the ossified rete. b. Cartilage of one of the interspaces, c. Cartilage 

 cells, with their nuclei, d. Newly formed Purkinjean corpuscles still containing the nucleus, e, A cell partly 

 enveloped in the deposit of the osseous salts. (From Nature, by J. L.) 



1 The account recently given by Prof. Kolliker of the formation of the lacunae, &c. is 

 too much founded, as it appears to the Author, upon observations made upon an abnormal 

 mode of it, which cannot be taken as the criterion of the healthy process. (See g 269.) 

 Some criticisms upon Prof. K's views will be found in the "Brit, and For. Med. Chir. 

 Rev.," Jan. 1852. 



* Sharpey and Quain, Anutoiuy. Edited by Leidy, vol. i. p. 91, Am. El. 



