12 OSSEOUS TISSUE. 



be extracted or isolated from the tissues, without any essential 

 change in their composition. We shall then notice the parenchy- 

 matous juices which permeate the tissues, provided they exhibit any 

 peculiar chemical relations. Without entering deeply into the 

 purely physiological relations of the individual tissues, we shall 

 then consider the question whether anything definite, regarding 

 the physiological function of the tissue, can be deduced from its 

 chemical constitution, in so far as it is yet known. 



Finally, we shall endeavour, at the conclusion of each subject, 

 to form, as it were, a basis for an introduction to a more general 

 chemical analysis from the results obtained by the micro-chemical 

 investigations. If our previous remarks on the chemistry of the 

 tissues have failed to demonstrate the great deficiency of our know- 

 ledge in this department, the analytical results will afford conclusive 

 evidence that we are still very far from being able to clothe histo- 

 chemistry in a rational garb, or to represent in a scientific form the 

 morbid changes of the tissues. 



OSSEOUS TISSUE. 



WERE we to consider the constitution of osseous tissue only 

 from a chemical point of view, without reference to its histological 

 conformation, we should scarcely arrive at anything like a correct 

 idea of bone. We must, in the first place, bear in mind that this 

 substance, which was formerly included amongst the simple tissues, 

 has not only a somewhat varying, but also a complicated texture, 

 in which, as in the tissues of a higher order, vessels and nerves 

 enter, and in which, as in other tissues, nutrient matter (or plasma) 

 and effete materials are met with. Without entering minutely into 

 the structure of osseous tissue, we must at all events remark that 

 this substance whether pertaining to the flat or the long bones 

 is penetrated by numerous cavities and canals which, in the fresh 

 bone, are not empty, and, in the dry, contain at least the non-volatile 

 constituents of the former contents. These cavities in the bones 

 are not merely those which are perceptible to the naked eye, as for 

 instance, the great medullary canal in the centre of the cylindrical 

 bones and the cellular spaces of the spongy bones, and the nutri- 

 tious foramina; in addition to these more obvious solutions of 



