bone. Of the former, we have a good instance in the minute structure of gouty bone, where, as we are informed by Mr. Ure,' the Haversian canals are enlarged, and choked up with cretaceous matter, which also lines the medullary canal; the osseous corpuscles are also found to be larger than usual, rather irregularly scattered, and less distinct, and their canaliculi loaded with chalk, which is shown by analysis to be true carbonate of lime, and not like the tophi of adjoining articulations, phosphate of soda; Mr. Ure states that he has found similar appearances in a femur of a person laboring under rheumatic arthritis. The latter, the rarefied state of bone, is that to which the term of osteoporosis was given by Lobstein. This is a condition3 commonly met with in rickety individuals, though it is also found in advanced life, in subjects who do not appear to be otherwise liable to rachitis. The affected bone presents an increase of size, and a diminution of density, owing to the tissue being expanded; the surface of the bone is irregular, and very porous. The periosteum, however, is not altered, nor do the surrounding textures exhibit any pathological changes. The medulla may be healthy, or changed in color and consistency. The canals of Havers, and the cells, will be found enlarged according to the seat of the injury, the gradual expansion inducing a thinning of the surrounding osseous layers, and eventually a communication between adjoining cavities. The condition may affect the compact or cancellous tissues alone or together. When the cortical layers are the seat of the change, the appearances may induce the resemblance of caries. Lobstein describes the surface in this case as being covered with a multitude of longitudinal fibres, resembling those of a foetal skull. He attributes them to the development and the action of the periosteal vessels, which hollow out for themselves channels in the osseous substance. When this variety of cortical rarefaction is raised above the surrounding tissue, it resembles one form of osteophyte, and many of the preparations of caries preserved in museums are referable to the same head. The rarefaction of the osseous tissue which constitutes osteoporosis, though often inducing a considerable increase of bulk, is essentially distinct from the process giving rise to the formation of exostosis, in which the generation of new osseous matter is the characteristic feature; the former being essentially an atrophic, the latter an hypertrophic, condition. The term spina ventosa, though one which has nothing but the prestige of antiquity to recommend it, is applied, among others, to affections belonging to the class just considered. We will not seek to perpetuate it by defining its characters, as it is an arbitrary designation, without any acknowledged and established meaning. Osteoporosis gives rise to fragility of the bones affected with it, and undoubtedly takes its origin in many of the dyscrasia which impair nutrition; though we meet with it occasionally in old age, as a mere effect of mal-nutrition, without any well-marked symptoms of a constitutional crasis, or of inflammatory action. An

1 Lancet, 1847.

2 In preparing sections of bone it is not unusual to employ putty powder; if some of this insinuates itself in the Haversian canals, we should necessarily find some carbonate of lime, which might mislead the observer.

3 See Lobstein, Anatomie Pathologique, vol. ii. p. 116.

analogy undoubtedly exists between the forms of disease just adverted to and mollities ossium, but the latter presents so peculiar a type, and

is so evidently removed from anything like a local affection, or from inflammatory causes, that we reserve its consideration for the sequel, and

Fig. 362.

now turn to examine the phenomena of suppuration, and the formation of abscess in bone. This may be diffused, or circumscribed, as in soft parts. It is secreted by the medullary membrane, and in its turn excites more or less reaction in the surrounding textures. The diffused form is the most dangerous, and may arise both from severe mechanical injury, and from constitutional causes. It is commonly associated with phlebitis. The pus occasionally penetrates the bone, and an escape having been thus effected, a cure may be brought about without loss of limb, though the partial death of the bone will necessarily result. In circumscribed abscess we find a cavity, generally in or near the epiphyses, lined with a vascular membrane. A process of condensation or ossification is seen to take place in the vicinity of the abscess, while there is thickening of the adjoining periosteum, and the surrounding cellular tissue. It is probable, as Mr. Stanley remarks, that circumscribed abscess is in some cases attributable to the softening of tubercular matter, analogous to a pulmonary vomica, and that the contents may be discharged, leaving a cavity resembling a tuberculous cavity of the lungs. The circumscribed abscess, to use the words of the same author, usually Limited internal ab remains of small size, but in some cases it has enscess in lower part of tibia. larged much beyond the natural limits of the bone. Section of bone.-Prepared Such an enlargement of the abscess is not the effect in Royal College of Surgeons' Museum. of simple expansion of the walls of the bone; for in some of these cases the osseous wall of the abscess has increased in thickness with the enlargement of the cavity. The process consists of the combined action of absorption on the inside of the abscess, and of osseous deposit on its outside, whereby its osseous walls may acquire any degree of thickness, according to the predominance of absorption in the one direction, or of deposit in the other.

CARIES.

Chronic suppuration accompanies ulceration of bone, or, as it is commonly called, caries, a slow absorptive process, which may occur in all bones, and every part of their structure, but is most liable to attack the cancellous tissue. The bone presents a more or less eroded and cribriform appearance, and while absorption removes the tissue at one point, the surrounding parts are more vascular and tumefied than in the normal state, and the adjoining bone is commonly the seat of new osseous deposit; or the softening process extends to a distance, and the bone is converted into a soft, pliable mass. The more the earthy matter has been absorbed, the fewer the number of osseous corpuscles that remain; until they disappear altogether, and in their place we see only a granular substratum, with faint traces of the lamellar structure. The secretion is of a sanious, acrid, and fetid character, owing to the decomposition which takes place, and which is of diagnostic value during life, in determining the

up

Fig. 363.

existence or non-existence of disease of the bone. The discharge also contains minute portions of bony matter, showing the disintegration that is proceeding; and it is very frequently mixed with a grumous, flaky matter, resembling tubercle, evidencing the scrofulous character of the disease. The discharge is apt to discolor the exposed bone, and itself become of a dirty brown, after exposure to air, as well as to blacken the tissues and probes brought into contact with it. Caries may commence in the interior of a bone, as well as on the surface. In the former case, it commonly makes its way outwards. When the caries is superficial, the Haversian canals are enlarged, and, to use Rokitansky's description, the tissues within them form, in part, a disorganized, soft, and shreddy mass, infiltrated with ichor, or spongy granulations, which easily bleed, grow from them luxuriantly, and advance outwards, over the rough surface of the bone, whilst, internally, they partially or completely fill the enlarged Haversian canals. In both cases, the bone appears porous or cancellous, but its color differs in the two. In the former, it is discolored by the contents of the Haversian canals; in the latter, it obtains various tints of red, from the color of the granulations. When caries affects cancellous tissue, the bone acquires a livid red color, especially if the granulations be at all abundant; it becomes soft, resembles a mass of flesh, traversed by a delicate and brittle bony skeleton, and is easily cut with a knife, or yields to light pressure with a finger; lastly, it becomes swollen. The analogy of caries to ulceration of soft parts, is manifested in the mode in which a cure is established, as well as in its destructive stages. A healthy stimulus being set up, the absorption is converted into a reproFig. 364.

Fig. 365.

Caries.

Fig. 366.

Example of caries in the metatarsal bone of the great toe. Two carious ulcers; each surrounded by interstitial absorption as well as by attempts at reparative effort.

ductive process; the granulations restore the lost parts, if the chasm does not offer too great a tax upon the system, or the cicatrix is formed with more or less loss of the original substance.

NECROSIS.

Though caries often accompanies necrosis, the latter is as distinct from the former, as mortification differs from the ulceration of soft parts. Necrosis consists in the death of a portion, or an entire bone, resulting from various internal or external causes, which destroy its vitality. The necrosed part presents a dead white or waxy hue, or a greater Fig. 367.

Necrosis of the head of the femur, acetabulum, and shaft, subsequent to amputation. A. Necrosed scets bulum and head, completely anchylosed and broken off at e from the neck. f, Remains of the articular sur faces, closely united. B. Neck, and upper part of the shaft. a, New bone; b, new bone undergoing necrosis; c, bone still containing blood vessels, and in various stages of inflammation; d, a membranous septum, marking the boundary of the dead and living bone.

intensity of discoloration passing through various shades of green, brown, and black; changes attributed to the influence of the atmosphere, or of the decomposing pus, though not necessarily due to either. The limits of the necrosed portion are not always easily defined, and, at all times, its outline is extremely irregular. It attacks chiefly the compact tissue, and is, therefore, most frequently met with in the shafts of long bones,