334 THE SOLIDS. 



It appears to me that Henle has misunderstood the struc- 

 ture, and consquently the nature of the formations noticed 

 by him : there can be little doubt but that these, in place 

 of being bundles of filaments composed of inelastic fibrous 

 tissue encircled with a spiral coil of elastic tissue, are in 

 reality hollow cylinders, vessels in fact in progress of form- 

 ation, consisting of, in the stage described by the German 

 physiologist, an inner transparent and apparently structureless 

 tunic, enclosed in a coil of elastic fibrous tissue. 



The correctness of this view is established by the very 

 convincing fact, that the tubular formation in the condition 

 just described may be traced up to the state of perfect blood- 

 vessels, some of which may also now and then be seen divid- 

 ing into branches, and containing, moreover, blood corpuscles. 

 Several of the stages of the development of these vessels are 

 seen in Plate XL. Jig. 3. 



DEVELOPMENT OF CELLULAR TISSUE. 



Exact observations are still required on the subject of the 

 development of both the elastic and the inelastic forms of the 

 cellular or fibrous tissue, and especially of that of the latter 

 form. Schwann and all other observers after him have 

 described the cellular tissue as taking its origin in cells of 

 an elongated form, from the extremities of which fibres, 

 mostly branched, proceed, the cells themselves ultimately be- 

 coming absorbed: microscopists, however, have not as yet 

 attempted to point out the differences which doubtless exist 

 in the development of the two forms of cellular tissue, but 

 have for the most part contented themselves with the above 

 general description. 



It appears to me that the observations already made on 

 the development of the cellular tissue apply only to the 

 yellow or elastic kind ; and to this conclusion I am led by 

 the fact that observers describe the elongated nuclei as giving 

 origin to branched filaments ; and we know that the fibres of 

 the inelastic fibrous tissue are simple, and not branched. 



