BOXE. 



Fig. LVIII. 



epiphyses is different in different bones ; in many it does not arrive until 

 the body has reached its full stature. Meanwhile the bone increases in 

 length by the ossification continuing to extend into the intervening 

 cartilage, which goes on growing at the 

 same time ; and it appears that in the 

 part of the shaft already ossified little or no 

 elongation takes place by interstitial growth. 

 This is shown by an experiment first made 

 by Dr. Hales and afterwards by Duhamel 

 and by John Hunter, in which, two or more 

 holes being bored in the growing bone of a 

 young animal at a certain measured distance 

 from each other, they are found after a time 

 not to be farther asunder, although the 

 bone has in the mean while considerably 

 increased in length.* In like manner the 

 shaft also increases in circumference by 

 deposition of new bone on its external sur- 

 face, while at the same time its medullary 

 canal is enlarged by absorption from within. 

 A ring of silver or platinum put round the 

 wing-bone of a growing pigeon, becomes 

 covered with new bone from without, 

 and the original bone included within it 

 gets thinner, or, according to Duhamel, 

 who first made the experiment, is entirely 

 removed, so that the ring comes to lie 

 within the enlarged medullary canal. 



Madder given to an animal along with its 

 food, tinges the earth of bone, which, acting as a 

 sort of mordant, unites with and fixes the colour- 

 ing matter. Now, that part of the bone which 

 is most recently formed, and especially that part 

 which is actually deposited during the admi- 

 nistration of the madder, is tinged both more 

 speedily and more deeply than the older part; 

 and, as in this way the new osseous growth 

 can be readily distinguished from the old, ad- 



Fig. LYIII. SUBPERIOSTEAL 



LAYER PROM THE EXTREMITY 

 OF THE BONY SHAFT OF THE 

 OSSIFYING TIBIA, AS DESCRIBED 



IN THE TEXT. 



The cartilage and more open 

 bony tissue have been scraped off 

 from the inside of the crust, ex- 

 cept at a, where a dark shade 

 indicates a few vertical osseous 

 areolae out of focus and indistinctly 

 seen. The part a, b, of the crust 

 is ossified, and of granular aspect ; 

 between 6 and c are the clear reti- 

 culated fibres into which the earthy 

 deposit is advancing. Magnified 

 150 diameters. 



vantage was taken of the fact by Duhamel, 



and afterwards by Hunter, in their inquiries as to the manner in which bones 

 increase in size. By their experiments it was shown that when madder is given 

 to a young pig for some weeks, the external part of its bones is deeply red- 

 dened, proving that the new osseous matter is laid on at the surface of that previously 

 formed. Again, it was found that, when the madder was discontinued for some time 

 before the animal was killed, an exterior white stratum (the last formed) appeared 

 above the red one, whilst the internal white part, which was situated within the red, 



* Hales, Veget. Statics., 4th edit. p. 340 ; Duhamel, Mem. de 1'Acad. des Sc., 1743 et 

 seq. Hunter (reported by Home) in Trans, of Soc. for Imp. of Med. and Chir. Know- 

 ledge, vol. ii. ; also Catalogue of Hunterian Museum, vol. i. p. 249. Duhamel Avas led 

 from some of his experiments to infer that an interstitial elongation took place near the 

 ends ; but there is some doubt left as to the precise circumstances of the experiments 

 in these cases. Both Hales and Duhamel, in experimenting on the growing tibia of a 

 chicken, observed that the addition of new bone was much greater at the upper end. Dr. 

 Humphry has found that in the femur the elongation is greater at the lower t and in the 

 humerus at the upper end of the shaft (Med. Chir. Trans, vol. xliv.). 



h 



