BONE, PATHOLOGICAL CONDITIONS OF. 



455 



But although we concede to the periosteum the 

 principal office in the process of reproduction, 

 we can also conceive that the adjacent tissues 

 are also more or less engaged, for the thicken- 

 ing of parts is found to extend on the outside 

 of this membrane, and Dr. Macartney himself 

 speaks of the cellular tissue external to the 

 periosteum becoming altered and condensed. 

 Now, supposing the periosteum to be destroyed, 

 these structures may be capable of supplying 

 its place and producing the secretion of gelati- 

 nous substance, which is afterwards to become 

 bone, just as we see that if the periosteum is 

 torn off a bone, the adjacent tissues laid down 

 upon it may prevent exfoliation, and answer 

 every purpose of nutrition and preservation 

 that the original membrane did. From what- 

 ever source derived, this deposition begins 

 while yet the original bone is in a state of in- 

 flammation, and the part that is to die still un- 

 detached. If tendons or muscles are inserted 

 into this part of the bone, they, being living and 

 organized substances, separate from that which 

 is dead : but the previous deposition has ex- 

 tended about them, and fastened them in their 

 situations, and hence not only is the limb capa- 

 ble of support during the progress of necrosis, 

 but unless in exceedingly rapid, acute, and un- 

 favourable cases, its motions may not be very 

 materially impaired. 



Soon after the investing shell has been form- 

 ed, the dead portion of the bone separates from 

 its attachments, and lies within its osseous 

 case. It is now termed the sequestrum, and 

 presents some remarkable and peculiar charac- 

 ters that distinguish it from diseased bone 

 otherwise circumstanced. Its extremities are 

 always jagged, pointed, and uneven : its mar- 

 row and internal periosteum have disappeared : 

 its length and its diameter are always much 

 less than ought to be anticipated from consi- 

 dering the size of the bone that has died ; and 

 its surface is uneven and marked with slight 

 depressions, as if part of its substance had 

 been taken up by the absorbents. This ap- 

 pearance is more distinctly observable, and the 

 sequestrum is always smaller where the surface 

 of the new shell is covered with granulation, 

 than when it is only smeared over with lymph. 

 And here, as in other cases, it may be observed 

 that the existence of granulation or of lymph 

 on the new bone seems greatly to depend on 

 the free admission of air to the cavity. Where 

 the bone is deep-seated, as in the thigh, and 

 there are but a few sinuous apertures that can 

 scarcely render the cavity analogous to an open 

 sore, the surface is covered by a layer of lymph; 

 but where it is more superficial, as when the 

 shaft of the tibia has come away and left the 

 new osseous deposit totally uncovered, its entire 

 surface is seen studded over with healthy gra- 

 nulations, which, on passing the handle of a 

 scalpel over them, are found to be gritty, and 

 give sensible indications of containing bony 

 matter. 



From the first formation of the new deposit, 

 small holes or perforations exist in it, the edges 

 of which are bevelled down and thin, and not- 

 withstanding that the new bone may and 



usually does become extremely thick and 

 spongy, these apertures still remain thin : it is 

 through them the matter makes its way to the 

 surface and forms the fistulous ulcers that 

 attend on this disease, and are to be described 

 bfereafter. These apertures remain as long as 

 there is a single spicula of sequestrum within to 

 keep up irritation and protract the suppuration. 

 After the sequestrum lias completely disap- 

 peared, the growth of osseous material still 

 continues internally until the new shaft appears 

 one solid mass devoid of any cancellated or 

 medullary cavity whatever. At this period the 

 ulcers are healed up, and the patient enjoys a 

 wonderful use of his swollen and deformed 

 limb, but the pathological condition of the bone 

 is still deserving of attention. At first it is a 

 mass of soft and spongy texture. After the 

 lapse of a few years, though still clumsy in 

 shape and undiminished in diameter, the bone 

 has become much more firm and solid, and in 

 these respects, at least, equals the original 

 structure. At a more remote period the osseous 

 part is wonderfully solidified, being, in some 

 instances, as firm as ivory, and a new medul- 

 lary cavity, with an internal periosteum, is 

 formed. When a transverse section of a tibia 

 so circumstanced is made, the osseous walls 

 are found to be hard, thick, and very firm, the 

 medullary cavity much narrower than in the 

 healthy bone, being scarcely capable of admit- 

 ting more than a goose-quill, and it does not 

 seem to be cancellated or reticulated, but merely 

 to consist of one continuous cell. In this state 

 the bone possesses nearly three times the 

 weight of one in the natural condition, and 

 when dried is of a dirty brown colour, never 

 assuming the white tint or polished appearance 

 of the remainder of the skeleton. 



Necrosis once formed is variable in its pro- 

 gress and indefinite as to the time that may be 

 necessary to its completion. Sometimes the 

 affection of the bone is exceedingly acute, ac- 

 companied by external inflammation resemb- 

 ling phlegmonoi'J erysipelas : in these cases 

 the bone soon dies, the sequestrum separates 

 and protrudes very rapidly, perhaps even before 

 the new deposit has attained strength to sup- 

 port the limb, so that it is necessary to preserve 

 it artificially as to shape and length until the 

 process is complete. Within the last year we 

 have seen a case in which, through neglect of 

 this precaution, the tibia is bent nearly into the 

 shape of the letter C. In other instances the 

 disease is extremely tedious, requiring years 

 before the sequestrum is either removed or ab- 

 sorbed : we possess a preparation exhibiting a 

 specimen of necrosis of more than six years' 

 duration, in which the sequestrum is of a more 

 than ordinary size. Between these extremes of 

 great rapidity and as great tediousness there is 

 every possible variety, and perhaps these me- 

 dium cases are the most unfavourable, for the 

 very rapid are over before the constitution is 

 broken down, and the very slow produce their 

 effects on the system so gradually as not to 

 make any decided or severe impression ; whilst 

 those which exhibit the symptoms of abscess, 

 with an extraneous body working to gain the 



