xcviii BONE. 



lamellae presents a corresponding appearance, for as the fibres run more or less 

 obliquely to the axis of the bone, they present cut ends in a longitudinal section also. 



It thus appears that the amimal basis of bone is made up of lamellae com- 

 posed of fine reticular fibres ; but interposed among these lamellae, layers are 

 here and there met with of a different character, viz. : 



1. Strata of amorphous or granular aspect, in which the lacunae are very 

 conspicuous and regularly arranged, and sometimes appearing as if sur- 

 rounded by faintly defined areol*e. These generally incomplete layers often 

 terminate by a scalloped border, as if made up of confluent round or oval 

 bodies; this is indicated also by the occasional occurrence of oval or flattened 

 spheroidal bodies singly or in small groups near the border of these layers, 

 each, with a cavity, apparently a lacuna, in the centre. In fact, if the 

 round bodies shown in figure XLVIII. had a central vacuity, they would 

 very well represent the objects here referred to. In some parts the granular 

 substance is obscurely fibrous, and transitions may be observed to the 

 well-marked reticular laminse. The layers described principally occur, so 

 far as I have been able to observe, near the surface of the compact 

 tissue, and at the circumference of many of the systems of concentric 

 Haversian lamellse. 



2. Irregular layers of rounded bodies, apparently solid and without central 

 cavity or mark, well represented in figure XLVIII., which is after a drawing 

 from nature by Dr. A. Thomson. I have hitherto met with these layers 

 chiefly near the surface of the shaft of long bones, lying among the circum- 

 ferential laminse, and, so far as I can observe, forming only part of a 

 circuit. They can occasionally be recognised in a transverse section as 

 short curvilinear bands of peculiar aspect, broader in the middle and thinning 

 away at the ends, appearing here and there between the cut edges of two 

 ordinary circumferential larmnse. 



The appearances described under 1 and 2, and especially the last, as represented in 

 fig. XLVIII., suggest the notion of irregular layers of spheroidal bodies, some single, 

 but mostly confluent in groups, adherent to the subjacent surface ; and one is especially 

 tempted to this belief by the account given by Gegenbaur * of the deposition of osseous 

 matter in growing bone at certain points in the form of oval or spheroidal globules, 

 which in size and aspect would sufficiently answer to the objects above described. 

 Nevertheless I incline rather to the explanation offered by Professor C. Loven, of 

 Stockholm, to whom I showed the figure and specimens ; viz., that the surface covered 

 apparently with globular bodies, single or in botryoidal groups, is really a cast in 

 relief from a contiguous surface of bone that has been excavated by absorption. It 

 is known that in the growth of a bone absorption occurs at various parts, and is often 

 followed by fresh ossific deposition; as, for example, in the excavation and subsequent 

 filling up of the Haversian spaces. The absorption in such cases is a healthy process, 

 but the absorbed surface is, as in absorption from disease, eroded or scooped out into 

 sinuous hollows, the larger of which are again carved on the inside into smaller 

 rounded pits. New osseous matter deposited on such a surface fills up its hollows, and, 

 when the new layer is detached, it exhibits a raised impression corresponding with 

 them.f 



* Jenaische Zeitschrift fiir Medizin und Naturwissenschaft. Vol. 1. p. 353. 



{ Two observations which I have had occasion to make favour this explanation. A 

 cross section of a (large) serpent's rib shows an outer and an inner series of concentric 

 lamellae surrounding the medullary canal, and the inner trenches on the outer by a festooned 

 border such as often bounds a series of Haversian rings. Now, in the decalcified rib, it is 

 easy to peel off the inner from the outer layers, and the detached surface of the former 

 shows a number of oval eminences, some with one, others with two, three, or more lacuna? 

 in their substance ; whilst what was the contiguous surface of the outer layers has exca- 

 vations that correspond. Again, in the grinding tooth of the horse, the surface of the 



