126 TRANSFORMATIONS OF NUCLEI 



minute vesicular bodies, in all respects similar to nuclei or cytoblasts, 

 exist in considerable abundance, and appear to be the essential parts 

 concerned in discharging the functions of these organs. And Professor 

 Goodsir's observations in several of his papers * seem to demonstrate 

 the power of the nucleus both in the production and multiplication of 

 cells, and in the formation and storing of secretions. 



The transformation of nuclei into higher tissues has been shewn espe- 

 cially by the researches of Henle,f and more recently by those of Kolliker.J 

 According to Schwann's system of cell-formation, the nucleus is supposed 

 to disappear shortly after the perfect state of the cell is attained. But the 

 results of recent observations have shewn that the disappearance of the 

 nucleus is of much more rare occurrence than was supposed by Schwann to 

 be the case, and, moreover, that instead of disappearing, the nucleus in many 

 cases assumes a higher degree of development, and is transformed into a 

 more or less persistent tissue. According to Henle, the only parts in 

 which the nucleus disappears are the blood-corpuscles, the cells of the 

 epidermis and the nails, and most of the fat-cells, the tubules of the 

 crystalline lens and of enamel, and many of the cartilage-corpuscles. 

 But in all fibres supposed to be formed from coalescing cells (except 

 those of the lens and enamel), the nuclei remain, and, moreover, undergo 

 remarkable transformations. For example, they assume an oval shape, 

 then gradually elongating and becoming narrow, are converted into fine 

 dark streaks, which lie in straight, angular, tortuous, or spiral lines upon 

 the fibres. After being thus changed they either gradually disappear, or 

 becoming more elongated and meeting with each other, they unite to form 

 a new set of fibres, which, from their mode of origin, he calls nucleus- 

 fibres. Occasionally these nucleus-fibres send off lateral branches, by 

 which a kind of continuous network is formed over the surface of each 

 layer of the tissue in which this arrangement occurs. Various other 

 modes of arrangement of these nucleus-fibres are observed in different 

 tissues. The fibres are remarkable for their dark well-defined outline, and 

 being insoluble, like other nuclei, in acetic acid, their existence and pecu- 

 liarity in a tissue may be at once ascertained by means of this re-agent. 

 Ordinary elastic tissue appears, according to Henle,|| to be only a variety 

 of such nucleus-fibres. 



Another remarkable purpose served by nuclei in the formation of tissues 

 has been pointed out by Henle as seen especially in the coats of blood- 

 vessels. In the development of these coats, layer after layer of cytoblas- 

 tema is deposited in the form of structureless membrane, and in each of 

 these, nuclei are shortly formed and undergo several different changes. In 

 the innermost layer cells grow around the nuclei, and thus is formed the 



* Op. cit. articles " Centres of Nutrition," "Secreting Structures," and * Serous Mem- 

 branes." f Allg. Anat. pp. 192 9. J Entwickelungs-ges. der Cephalopoden, p. 145. 

 $ Allg. Anat. p. 192. || Allgemeine Anatomic, p. 407. 



