280 SPECIAL HISTOLOGY. 



of a lacunae, together with the radiating canaliculi belonging to it, forms 

 an imperfect sphere, having a diameter of from 0*02 to 0-034 of a line; 

 with reference to which, however, it must not be forgotten, that individual 

 canaliculi transgress the usual length of the others, as I have, in fact, 

 measured anastomoses between two lacunae of the length of 0-04-0-045 

 of a line. 



The contents of the lacunce, according to the later investigations of 

 Bonders, Virchow, and myself, appear very closely to resemble those of 

 the cells of cartilage during life ; that is to say, they are clear, probably 

 viscid fluid, with a nucleus. If bone-cartilage be boiled in water or 

 caustic soda for 1 or 2 minutes, these nuclei often show themselves very 

 distinctly; or opaque corpuscles make their appearance, which must be 

 regarded as the contracted cell-contents including the nucleus, and analo- 

 gous to the corpuscles in cartilage. A peculiar phenomenon is seen to 

 occur, when bone is macerated in hydrochloric acid, which was first 

 noticed by Virchow in a diseased, and afterwards in healthy bone, and 



by myself in the cementum of the horse's tooth, 

 the lacunae become isolated, having longer or 

 shorter processes, and appear like independent 

 structures, or a sort of stellate cells. This 

 phenomenon seems to depend simply upon the 

 circumstance, that the tissue immediately sur- 

 rounding the lacunae offers more resistance to 

 the action of the acid than it does elsewhere. 

 In the cementum of the horse's tooth, cells also 

 enclosing the lacunae, and even Haversian ca- 

 nals, may be isolated, the best proof, that everything which thus pre- 

 sents itself in an isolated form, is not necessarily a morphological unity.* 



FIG. 119. A bone spicule from an apophysis, with distinct lacunae and nuclei. Boiled in 

 water, and magnified 350 diameters. 



* [It is of very great importance in histology to keep in mind the caution expressed in 

 the last paragraph of the text (see below, note 101), which applies as well to optical as to 

 chemical distinctness. 



Tomes and De Morgan assert that both the lacuna and canaliculi have parietes, which are 

 manifested by appearances similar to those observed in the dentinal tubes. They some- 

 times found the lacuna and canaliculi filled up to a great extent with solid matter, so as to 

 leave only a small space in the centre. 



An important modification of the lacuna, is described and figured by these authors (1. c., p. 

 8) in the circumferential laminje. Elongated tubes pass, in bundles or singly, more or less 

 obliquely from the surface towards the interior of the bone. When long, they are sometimes 

 bent once or twice at a sharp angle. They have parietes, and are connected laterally with 

 the canaliculi. They occur irregularly in the circumferential laminae, and in these only. 

 [Similar tubes exist in the cementum of the Teeth.] 



We can confirm Messrs. Tomes and De Morgan's statement that the nuclei may be found 

 without difficulty in recent^bone, and they may always be brought out with great distinctness 

 by the action of dilute hydrochloric or strong acetic acid. This is especially the case in 



