10 HISTO-CHEMISTRY. 



called for from those pathologists who imagine that a pathological 

 histo-chemistry may be hurriedly built up on a few insecure props, 

 and who have obscured the few exact chemical facts which we 

 possess regarding morbid tissues with their own nebulous hypo- 

 theses. 



If, however, we would extend to histo-chemistry our inherent 

 tendency to general abstractions, we may consider the general 

 proposition (laid down in vol. i, p. 25), that the physiological 

 importance of a substance is dependent on its chemical consti- 

 tution, as being equally well established, in so far as our experience 

 goes, in regard to the tissues ; for we merely express the simple 

 result of positive experience, and the inductions deduced there- 

 from, when we assert that the chemical nature of the tissues inva- 

 riably corresponds with their functions. It has been long known 

 that those tissues which are of service in the animal body almost 

 solely from their physical properties (their hardness, toughness, 

 elasticity, &c.), contain as their most essential basis a substance 

 which on boiling yields gelatin ; we further know that those 

 textural elements which are remarkable for a high degree of elas- 

 ticity, as the nucleated fibres of connective tissue and the true 

 elastic tissue, present a perfectly similar chemical relation ; and as 

 we gradually develope the subject of histo-chemistry, we shall have 

 convincing evidence that those tissues which exhibit special vital 

 activity those, namely, which, in addition to a slight but very 

 perfect elasticity (Ed. Weber), possess the power of contracting in 

 consequence of certain influences transmitted through the nerves 

 contain, as a matrix and essential constituent, one and the same 

 substance, muscle-fibrin or syntonin ; here we must place the 

 fibre-cells of those tissues which are specially known as " con- 

 tractile," and of smooth muscle, and the cylindrical fibres of 

 striped muscle. The arrangement and the chemical character of 

 the substrata constituting the nervous system, confirm rather than 

 oppose the above proposition, and afford a new proof that the 

 material substrata of the tissues are always constructed in chemical 

 conformity with their vital functions. 



There is one more circumstance which must not be left alto- 

 gether unnoticed, and which probably stands in a nearer connexion 

 with the above subject than might at first sight be supposed ; we 

 refer to the fluids permeating and bathing the tissues. We have 

 already seen that there are great differences in the chemical 

 character and composition of the fluids moistening the different 

 classes of tissues, the peculiarities of the fluid being apparently 



