274 SPECIAL HISTOLOGY. 



surface, ave less distinctly apparent, whilst the lamellar structure is very 

 manifest, and most generally two layers may be noticed in each lamella, 

 though by no means so clearly as shown in Fig. 113.* In sections 

 parallel to the surface, the bone, in many situations, appears almost 

 homogeneous throughout, presenting no trace of a granular structure, 

 whilst in others a structure of that kind is obscurely visible, together 

 with minute points (Deutsch), and besides these a longitudinal striation ; 

 which last gives the whole a fibrous aspect. From this circumstance, 

 many authors appear to have been led to describe the bone as composed 

 of fibres, but quite incorrectly, for although the study of their develop- 

 ment shows, that the ossifying parts are, to a certain extent, very dis- 

 tinctly fibrous, it is impossible to demonstrate anything of the sort in 

 perfect bone. On the other hand, there is no doubt that a coarsely 

 fibrous appearance exists, and especially in the bone-cartilage of the 

 compact substance, as has already been remarked by others, and which 

 is probably due to the fibrous fasciculi of the original blastema ; care 

 however should be taken not to look upon longitudinal sections of 

 lamellae as such fibres. f When bone is burnt and the fragments crushed, 



* [According to Tomes and De Morgan, the lamince, when well developed, are always 

 constituted of two portions, — an outer, highly granular, often composed of a single line of 

 large granules, and an inner, which is singularly clear and transparent, and to all appear- 

 ance witliout graiuilation or any recognizable structure. This distinct separation into two 

 layers, however, does not always exist; and in a complete Haversian canal, the iimermost 

 lamina of all is frequently clear, glassy, and structureless. 



The circumferential laminas are not so constantly present as is generally supposed, and 

 they rarely entirely surround the shaft of a long bone, still more rarely the flat bones. In 

 the fast-growing bones of young animals they are absent, while in adults they are usually 

 well developed in some jiarts ; so that their presence seems to indicate that the bone is 

 nearly stationary in its growth. In young, rapidly growing bone, the circumferential laminje 

 are replaced by a series which may be called the undidaling lamina. The surface of the 

 bone sends oft' processes, formetl of reduplicated lamince, which eventually arch over and 

 enclose those vessels of the periosteum which lie nearest them. The spaces thus formed 

 become the seat of Haversian systems. Young growing bone, therefore, may be distinguished 

 from that of adult animals, by its being composed of Haversian systems with intervening 

 unilnlating laminse. (Tomes and De Morgan, b. c, pp. 4-G.) — Tes.] 



■)■ [Messrs. Tomes and De Morgan (1. c, pp. 13, 14) adduce very good reasons for believ- 

 ing that the fibrous appearance which may often be detected in the laraince of bone arises 

 from imperfect illumination and definition, and express their belief that bone substance "is 

 composed of granules or granular cells, imbedded in a more or less clear, homogeneous or 

 subgranular matrix." They go on to say, " Thus as regards the basement, homogeneous 

 tissue, it will be found that where lamination is highly developed, the laminee have a trans- 

 parent and structureless, and a more opaque and granular part, to which the former appears 

 to be the matrix. The peripheral lamina of the Haversian systems is generally clear and 

 free from granularity, and the internal lamina sometimes presents a similar structureless 

 appearance. The matter which fills up the Haversian systems in the full-grown antlers of 

 the CervidfE aflbrds another and a very striking example of transparent structureless osseous 

 tissue, which in this instance is the more distinct, from the absence of canaliculi in its sub- 

 stance. Then, again, we have another instance in the clear tissue which is sometimes found 

 between the superficial Haversian systems of ordinary bone. It has already been described 

 as a non-laminated element found on the surface of certain bones. In the instances already 

 cited, and no doubt in many others which may be fountl in the skeletons of the lower ver- 



