MINUTE STRUCTURE OP BONE. 259 



cavity. The lacunae present some variety of figure, but in such a section as that 

 represented they for the most part appear irregularly fusiform, and lie nearly in the 

 same direction as the lamellae between which they are situated ; or, to speak more 

 correctly, they are flattened and extended conformably with the lamellae ; for when 

 the bone is cut longitudinally, their sections still appear fusiform and are still more 

 lengthened out in the direction of the lamellae. The canaliculi, on the other hand, 

 pass across the lamella?, and they communicate with those proceeding from the next 

 range of lacunae, so as to connect the little cavities with each other ; and thus since 

 the canaliculi of the most central range open into the Haversian canal, a system of 

 continuous passages is established by these minute tubes and their lacunas, along 

 which fluids may be conducted from the Haversian canal through its series of sur- 

 rounding lamellae ; indeed, it seems probable that a chief purpose of these minute 

 passages is to allow nutrient matter to be conveyed from the vascular Haversian 

 canals through the mass of hard bone which lies around and between them. In like 

 manner the canaliculi open into the great medullary canal, and into the cavities of 

 the cancellated texture ; for in the thin bony parietes of these cavities lacunae are 

 also contained ; they exist, indeed, in all parts of the bony tissue. The canaliculi 

 which radiate outwards from the lacunae near the periphery of the Haversian systems 

 do not as a rule communicate with those of the neighbouring Haversian system, but 

 bend round and are joined to one another. 



Cells of bone. As first shown by Virchow, each lacuna is occupied by a 

 flattened nucleated cell, which sends branches along the caualiculi ; and later 

 observers (Rouget, Neuman,) have been able to detach the proper wall of the lacuna 



Fig. 299. A BONE-CELL ISOLATED AND HIGHLY MAGNIFIED 



(after Joseph). 



a, proper wall of the lacuna, shown at a part where the cor- 

 puscle has shrunk away from it. 



and its appertaining canaliculi after decalcification, 

 and to obtain it separate with its included corpuscle 

 (fig. 299). It can scarcely be doubted that the pro- 

 toplasm of the nucleated corpuscle takes an important 

 share in the nutritive process in bone, and very pro- 

 bably serves both to modify the nutritive fluid supplied 



from the blood and to further its distribution through the lacunar and canalicular 

 system of the bony tissue. Virchow showed that the corpuscles of bone are homo- 

 logous with those of ordinary connective tissue : to this it may be added that the 

 enclosing lacunae and canaliculi are to be looked upon as corresponding to the cell- 

 spaces of that tissue. 



Apertures and decussating fibres of the lamellae. With a little pains 

 thin films may be peeled off in a longitudinal direction from a piece of bone that 

 has been softened in acid. These for the most part consist of several lamellae, as 

 may be seen at the edge, where the different layers are usually torn unequally, and 

 some extend farther than others. Examined in this way, under the microscope, 

 the lamellae are seen to be perforated with fine apertures placed at very short 

 distances apart. These apertures were described by Deutsch l ; they appear to be the 

 transverse sections of the canaliculi already described, and their relative distance 

 and position accord sufficiently with this explanation. According to this view, there- 

 fore, the canaliculi might (in a certain sense) be conceived to result from the apposi- 

 tion of a series of perforated plates, the apertures of each plate corresponding to those 

 of the plates contiguous with it ; or they might be compared to holes bored to some 



1 De Penitiori Ossium Structurd, Wratisl. 1834, p. 17, Fig. 6. 



