DR. BEALE, OX THE TISSUES. 19 



The stclliitc cells are stellate from the very beginning. 

 The bone cell is never stellate at any period of its existence. 

 The tubes in the first case contain germinal matter. The 

 tubes in bone are merely spaces left between the particles of 

 calcareous matter which are deposited in the matrix, and for 

 this reason do not exist in the formed material of bone or 

 cprtilage prior to the deposition of calcareous matter. They 

 are present when calcareous matter is deposited in cartilage. 

 The dentinal tubes correspond to the processes from, and the 

 cavities of, the stellate cells, but they differ entirely from the 

 canaliculi of bone. The so-called tubes in the stellate tissue 

 and in dentine are no more tubes than the space filled with 

 germinal matter in an elementary part — say of the cuticle — 

 is a cavity. Spaces remain if the germinal matter is removed ; 

 but during life these so-called tubes and spaces are occupied 

 with the most important part of the whole structure, — the 

 living, active-growing germinal matter. The canaliculi of bone, 

 therefore, do not correspond to the above tubes or spaces; 

 they do not contain at any period of their formation germinal 

 matter. They are mere channels left during the deposition 

 of calcareous particles in the formed material. 



These channels in bone are, no doubt, subservient in a 

 very important degree to the rapid changes which occur in 

 this hard tissue. The bone tissue could not be so rapidly 

 formed or so quickly removed if it were not freely permeated 

 by canals. In dentine the formed material becomes much 

 more slowly impregnated with calcareous matter and incor- 

 porated with the organic matter, so that a very hard, even, 

 and very permanent structure results in which pores exist 

 only in certain parts, especially in the granular layer of the 

 dentine. 



In all cases the formed material is impregnated with cal- 

 careous matter from without inwards. The necessity for the 

 existence of bone at a very early period of development, the 

 gradual alteration in the size of the bones during the growth 

 of the body, and the changes in their form seem to be in- 

 compatible with a mode of development like that by which 

 dentine is produced. 



While Virchow has been led by his researches to the con- 

 clusion that nutrient tubes exist in connexion with cells in 

 soft tissues, the results of Dr. Beale^s observations have com- 

 pelled him to conclude that such tubes do not exist in soft 

 tissues as tubes for the transmission of nutrient material, 

 and that even the so-called dentinal tubes are not nutrient 

 canals; while it appears that the canaliculi of bone which 

 are of this nature do not correspond to the dentinal tubes. 



