096 



MINUTE STRUCTURE OF BONE. 



latter are remarkable for tlieir angularity of form and the fewness 

 of their radiations, — as shown in Fig. 357 5 which represents the 



Fig. 357. 



Section of the Bony Scale of Lepidosteus : — a, showing the 

 regular distribution of the lacunae and of the connecting canali- 

 culi ; b, small portion more highly magnified. 



Lacuna? and Canaliculi in the bony Scale of the Lepidosteus ('bony 

 pike' of the North American lakes and rivers), with which the 

 bones of its internal skeleton perfectly agree in structure. The 

 dimensions of the Lacunae in any bone do not bear any relation 

 to the size of the animal to which it belonged ; thus there is little 

 or no perceptible difference between their size in the enormous 

 extinct Iguanodon and in the smallest Lizard now inhabiting the 

 earth. But they bear a close relation to the size of the Blood- 

 corpuscles in the several Classes ; and this relation is particularly 

 obvious in the ' perennibranchiate' Batrachia, the extraordinary 

 size of whose blood-corpuscles will be presently noticed (§ 555): — 



Proteus 

 Siren . 

 Menopoma . 

 Lepidosiren . 

 Pterodactyle 



Long Diameter. 

 1-570 to 1-980 

 1-290 to 1-480 

 1-450 to 1-700 

 1-375 to 1-494 

 1-445 to 1-1185 



Short Diameter. 

 1-8S5 to 1-1200 

 1-540 to 1-975 

 1-1300 to 1-2100 

 1-980 to 1-2200 

 1-4000 to 1-5225* 



544. In preparing Sections of Bone, it is important to avoid the 

 penetration of the Canada balsam into the interior of the Lacunas 

 and Canaliculi ; since, when these are filled by it, they become 

 almost invisible. Hence it is preferable not to employ this cement 

 at all, except it may be, in the first instance ; but to rub-down 

 the section beneath the finger, guarding its surface with a slice of 

 Cork or a slip of Gutta-percha (§ 141) ; and to give it such a polish 



* See Prof. J. Quekett's Memoir on this subject, in the "Transact, of 

 the Microsc. Soc," Ser. 1, Vol. ii. ; and his more ample illustration of it 

 in the " Illustrated Catalogue of the Histological Collection in the Museum 

 of the Royal College of Surgeons," Vol. ii. 



