TISSUES, ORGANS, AND SYSTEMS. 85 



closely surround a generally elongated nucleus, and are partly united 

 into fibres or networks. With regard to the development of these cells, 

 Virchow deduces from Schwann's observations, and Donders from his 

 own investigations, the result that the well-known fusiform cells in the 

 rudimentary areolar tissue of embryos are nothing more than the forma- 

 tive cells of the so-called nucleus-fibres ; to which, then, as a conse- 

 quence, it is added that the proper connective tissue does not proceed 

 from cells, but is nothing else than fibrillated cytoblastema. Hence 

 both these authors agree in placing connective tissue and cartilage side 

 by side and, in comparing the formative cells of the so-called nucleus- 

 fibres, which Virchow calls " connective-tissue corpuscles," (Binde- 

 gewebskb'rperchen), with the cartilage-cells ; the interstitial substance 

 of the cartilage, with the fibrous part of the connective tissue. Virchow 

 goes still further, and compares even the bone substance to connective 

 tissue ; especially that which is developed by the ossification of what I 

 have called soft blastema, in which the bone cavities, he supposes, pro- 

 ceed from stellate anastomosing " connective-tissue corpuscles," a view 

 which seems chiefly to have led him to declare that the nucleus-fibres 

 are hollow, and form a great system of tubules and cavities through the 

 connective tissue, thus probably subserving nutrition. It could be 

 imagined that the nutritious fluid might thus be quickly conducted for 

 considerable distances, and uniformly distributed through the tissue, in 

 which case the nuclei must be considered to be the special regulative 

 portions of the apparatus, while the cells are simply conductors. 



If we submit these different views to the test of observation, it results 

 that much is quite correct, but that some points are untenable. It is 

 true, that the so-called nucleus-fibres are developed from cells ; and the 

 fact is, indeed, noted in certain earlier statements and figures of Valen- 

 tin, Hassall, Quekett, and others. In the tissues of full-grown animals, 

 it is in many localities unquestionably impossible, in others very diffi- 

 cult, to attain to certainty upon these points, because here, even when 

 the nucleus-fibres still present indications of cells, the cell-membrane so- 

 closely embraces the elongated and by no means vanished nucleus, that 

 it is often quite out of the question to decide whether we have a cell 

 with two or more slender processes, or a fusiform or stellate nucleus ; 

 on the other hand in young animals, in which also Virchow made his 

 first observations, and especially in embryos, it is easy to come to a 

 clear decision upon the matter. In man, I find the tendons, ligaments, 

 and the aponeurosis palmaris and plantaris, to be especially serviceable 

 objects ; but in all the places in which elastic tissue is mixed with con- 

 nective tissue, I was able to follow their development. The observation 

 is most successful in the foetus of three to four months. Here, in all 

 the more solid organs composed of connective tissue, tendons, liga- 

 ments, fasciae, corium, the proper connective-tissue fibrils are already 



